Calculating distances between locations (geopoints) in Survey123 with the Haversine Formula

October 5, 2017October 13, 2017 dlengtonLeave a comment

Consider the scenario where a person is applying for a liquor licence and the law stipulates: New liquor premises must be located at least five hundred meters (500m) away from schools, places of worship; recreation facilities, rehabilitation or retreat centers, residential areas and public institutions.

For this requirement Survey123 can be a valuable tool and in this blog post I will show you how you can enable this functionality in a Survey123 form:

Step 1: Create a new survey with Survey123 Connect

Step 2: Create a geopoint field in the main survey which will be used to capture the location of the new licence premises

Step 3: Create a repeated section to capture the occurrences of nearby schools, places of worship etc. Each with a premise type and a geopoint

Your survey design should look similar to this:

type	name	label
geopoint	new_licence_location	New Licence Location
begin repeat	nearby_places	Nearby Permises
select_one category	place_type	Type of Premises
geopoint	nearby_location	Nearby Location
end repeat

Step 4: Now, split both the coordinates sets into their x,y pairs and convert them to radians:

calculate	gps_lat	gps lat	pulldata(‘@geopoint’, ${new_licence_location}, ‘y’) * pi() div 180
calculate	gps_long	gps long	pulldata(“@geopoint”, ${new_licence_location}, “x”) * pi() div 180

Do the same for the nearby_location geopoint field.
Step 5: Use the X, Y pairs to perform the distance calculation (in meters) with the Haversine formula:

acos(sin(${gps_lat_end})*sin(${gps_lat}) + cos(${gps_lat_end})*cos(${gps_lat})*cos(${gps_long}-${gps_long_end}) ) * 6371000

After having made some cosmetic enhancements and adding the 500m stipulation your survey should look like this:

DistanceCalcScreen

Feel free to use and adapt as you require. Here is a link to the Survey123 Excel design file: Licence Application

Leveraging data-as-a-service with the ArcGIS JavaScript API

October 2, 2017 richard@esriLeave a comment

Welcome to the information age! We are part of a lucky generation to be living in a time of great technological change. All around us, data and information about the world is being collected and collated, just waiting for someone to take advantage of it. Based on a recent demonstration we provided to a group of enthusiastic startups, this blog post looks at how to pull in some publicly available data via web services into a basic ArcGIS web app. We are going to use the Public transport data for emerging cities from wheresmytransport through a simple Restful web service.

We will build a basic web (but mobile-ready) app that locates the user and identifies the 10 nearest public transport stops and shows them on a map.

So, where do we begin? With the map of course!

1. Create a web app stub

Open a new project/page in your favourite web development IDE (I still just use notepad++) and create a basic framework for an app. We will pull in the ArcGIS JSAPI and related CSS, a simple HTML structure with some associated CSS classes for controlling how the app will look.

<!DOCTYPE html>
<head>
<title>Find My Nearest Transport Stops</title>
<!-- GET ESRI JAVASCRIPT API AND RELEVANT STYLE SHEET -->
<link rel="stylesheet" href="https://js.arcgis.com/4.4/esri/css/main.css">
<script src="https://js.arcgis.com/4.4/"></script>
<style>
#wrapper {
	position: absolute; 
	top: 0; left: 0; right: 0; bottom: 0; 
	background-color: rgb(237,242,245); 
	overflow: hidden;
}
#map {
	position: relative;
	width: 100%;
	height: 100%;
}
</style>
</head>

<body>
<div id="wrapper">
	<div id="map"></div>
</div>
</body>
</html>

You wont see much when opening this, but here is a tip for how I view and debug my “mobile-ready” apps – open Chrome Developer tools (F12) and toggle the device toolbar. Dock the dev tools window to the right and choose an appropriate mobile device from the drop-down. You can now easily view your app and follow the console alongside.

2. Add a map control

Using the JSAPI that has been loaded, follow the basic steps for creating a WebMap from an ArcGIS Online web map ID, add it to a MapView and assign it to the dom node you just created called “map”. Place the following code inside a script tag in the document header.

require(["esri/views/MapView","esri/WebMap","dojo/dom","dojo/domReady!"], 
	function(MapView, WebMap, dom) {	
		var webMapID = "d46eaef12c0a4864aec85c8708446f00"; // replace with your web map's ID
		
        // create web map from existing web map ID on ArcGIS Online
		var map = new WebMap({
			portalItem: {
				id: webMapID
			}
		});	
		console.log("Loading map: " + webMapID);

		// add the web map view and hitch to a dom node
		var view = new MapView({
			container: "map",
			map: map
		});
			
		// wait for map to be loaded
		view.then(function(){
			console.log("...Map resources have been loaded successfully.");				
		}, function(error){
			// Use the errback function to handle when the view doesn't load properly
			console.log("The view's resources failed to load: ", error);
		});
	}
);

If you are using the Chrome Developer tip I mentioned, you should see something like this.
Web App - Step 2

3. Add “find me” button
HTML5 provides a handy geolocation API for getting the user’s location based on the best available method on the device. Esri has packaged this method into a simple widget that makes it easy to add to a map. Note that in v4.x of the JSAPI you can now add items to the “ui” of the map using the “view.ui” properties. To add the widget, insert the following code into the main function that will load the widget, add it to the UI and set up a handler that zooms and centres the map to your coordinates.

function addMyLocationButton() {
	console.log("Adding my location button.");
	var gl = new GraphicsLayer();
	map.add(gl);

	var locateWidget = new Locate({
	  view: view,   // Attaches the Locate button to the view
	  graphicsLayer: gl,  // The layer the locate graphic is assigned to
	  goToLocationEnabled: false	// override this to control the zoom level on goto
	});
	view.ui.add(locateWidget, "top-right");
	locateWidget.on("locate", function(event){
		// event is the event handle returned after the event fires.
		console.log("Located your position at: " + event.position.coords.latitude + ", " + event.position.coords.longitude);
		console.log("Taking you there now.");
		view.center = new Point({x: event.position.coords.longitude, y: event.position.coords.latitude, spatialReference: 4326});
		view.zoom = 13; 
	});
}

TIP: don’t forget to add the new requires: “esri/widgets/Locate”,”esri/layers/GraphicsLayer”

And, then call the new function once the map has loaded (i.e. within the “view.then(function(){“ function).

addMyLocationButton();

Your output should look a little like this after clicking the new button:
Web App - Step 3

4. Get stops from wheresmytransport
First, I recommend going to check out wheresmytransport.com and read up on their cool data service that provides real-time access to consolidated public transport information in many major global cities (including Joburg and Cape Town). Use of their API is free if you sign up as a developer here: https://developer.whereismytransport.com/ – you will need to do this to get a client id and secret to run the app.
Now, we will add a new button that will call the service by adding the following code into your main function:

view.ui.add({
	component: "stopsButton",
	position: "bottom-right",
	index: 0
});
console.log("Get stops button added to the UI");

And add a dom node to host the new button to the HTML body:

<div id="stopsButton" class="esri-widget-button esri-widget esri-interactive" role="button" tabindex="4" title="Get stops">
		<span class="esri-icon esri-icon-map-pin" role="presentation" aria-hidden="true"></span><span class="esri-icon-font-fallback-text">Get stops</span>
</div>

Now that we have a button, let’s listen for it’s click event and then call the wheresmytransport service – by adding this code to the main function:

setTimeout(function () { // short delay to wait for the ui element to be loaded into the DOM, then attach an event listener for the click event
		
	document.getElementById("stopsButton").addEventListener("click", function(){
		console.log("Get Stops button clicked.");		
	});
}, 100);

Now, before you can use the wheresmytransport service, you need to request a security token. Add this code into the function you just created.

// get API token						
	console.log("Getting WMT secure token...");
	var CLIENT_ID = 'enter your client ID here from the developer portal';
	var CLIENT_SECRET = 'enter your client secret here from the developer portal';
	var payload = {
		"client_id": CLIENT_ID,
		"client_secret": CLIENT_SECRET,
		"grant_type": "client_credentials",
		"scope": "transportapi:all"
	};

	var request = new XMLHttpRequest();
	request.open('POST', 'https://identity.whereismytransport.com/connect/token', true);
	request.setRequestHeader('Accept', 'application/json');
	request.onreadystatechange = function () {
		if (request.readyState == 4 && request.status == 200) {
			var response = JSON.parse(request.responseText);
			//console.log('WMT token: ', response.access_token);
			console.log('...WMT token created successfully.');
			var token = response.access_token;
			localStorage.setItem('token', token);
		
			// now, with the token, go get the nearest stops
			getStops(token);	

			// and log the request
			//logRequest(view.center);
		}
	};

	var formData = new FormData();
	for (var key in payload) {
		formData.append(key, payload[key]);
	}
	request.send(formData);

You will notice that the successful callback runs a new function called “getStops(token)” to which it passes that new token. The getStops function looks like this.

function getStops(theToken) {
	console.log("Loading stops from wheresmytransport...");		
	var payload = {
		"point": view.center.latitude +","+ view.center.longitude,
		"radius": 1000
	};
		
	// convert the payload into url parameters
	var payloadParams = Object.keys(payload).map(function(key) { return key + '=' + payload[key]; }).join('&');
	var getLocalStops = getWMTdata('stops', payloadParams, theToken);		
}

This code only sends the request, now we need to handle the response by adding “then” and “catch” callbacks for the promise variable we created called “getLocalStops”. This code will process the results by creating a new Esri graphic and adding to the graphics layer with the specified symbology.

getLocalStops.then((successMessage) => {
	var theStops = JSON.parse(successMessage);
	console.log("..." + theStops.length + " stops successfully loaded.");
	console.log("Now creating map features.");
				
	graphicsLayer = new GraphicsLayer();
	var stopSymbol = new SimpleMarkerSymbol({
		style: "circle",
		color: "yellow",
		size: "8px",  // pixels
		outline: {  // autocasts as esri/symbols/SimpleLineSymbol
		color: [ 255, 255, 0 ],
			width: 1  // points
		}
	});
				
	theStops.forEach(function(stop, i){
		// create a new graphic object for each result (stop)
		graphicsLayer.graphics.add(new Graphic({
			geometry: new Point({x: stop.geometry.coordinates[0], y: stop.geometry.coordinates[1], spatialReference: 4326}),
			symbol: stopSymbol,
			attributes: {
				name: stop.name,
				modes: stop.modes.toString(),
				agency: stop.agency.name
			}
		}));
	});
	// now add the graphics layer to the map			
	map.add(graphicsLayer);
				
});
getLocalStops.catch((errorMessage) => {
	console.log(errorMessage);
});

TIP: Remember to add the new requires “esri/symbols/SimpleMarkerSymbol”, “esri/Graphic” and “esri/geometry/Point”

Finally, for the eagle-eyed among you, there is a utility function called from within the code called “getWMTdata” that takes the url, token and payload which you can use generically for calls to those services.

function getWMTdata (url, payload, token) {	
	return new Promise((resolve, reject) => {
		var request = new XMLHttpRequest();
		request.open('GET', 'https://platform.whereismytransport.com/api/' + url + "?" + payload, true);
		request.setRequestHeader('Accept', 'application/json');
		request.setRequestHeader('Authorization', 'Bearer ' + token);
			
		request.onload = () => resolve(request.responseText);
		request.onerror = () => reject(request.statusText);
		request.send(null);
	});		
}

That’s it. Run the app and after clicking both the “Locate Me” and the “Get Stops” button, your app should look a little like this:
Web App - Step 4

5. Take it further…
This is a basic example, but think about how you can take this app further, by adding capabilities such as:

Finding the nearest stop based on travel distance/time using the FindNearest method from ArcGIS
Display results back to the user in a table or list for easy viewing
Log requests made by users to be able to assess where the demand for the app is…
Many many more!!

If you would like to try out the sample code, you can download this example here. Let me know in the comments below if you want some more info/help!

Happy app-making

– Richard

SCHOOL EARLY WARNING SYSTEM

August 16, 2017 KabeloLeave a comment

The North-West Department of Education and Sport Development is one of the largest departments having staff complement of 30000 and serving 800000 learners annually.

The department have a need to respond to the needs of schools on the ground. This has resulted in a need for a department to require a solution that will follow a systematic approach of reporting and recording incidence and emergencies occurring at schools. The solution should enable real time incident recording and must have the ability to send alerts to the department’s officials, thus enabling the department to promptly respond to the needs of schools. This has triggered a need for the optimal implementation of the ArcGIS Platform to support these development initiatives.

The North-West Department of Education and Sport Development is a huge administration with diverse products and service offering especially to the schools. The biggest challenge that is faced by the department is the turnaround time on issues raised by any sector at any given time. The current method of disseminating information is primitive and non-effective because it’s still relying the most on paper methods.

The implementation of the platform should assist the operations within the department, but also establish standards that will ensure interoperability and integration of data, systems and other GIS resources.

Each school would require access to the solution through the principal or management of the school. The people assigned would be responsible to communicate incidents through the solution, this should give the department the best chance to respond with effective reaction times.

*Spatial view of Schools with Incidents*

The solution identified for these specific requirements was School Early Warning System. The Esri platform forms and integral part of the development of this system. The platform provides a spatial data infrastructure within the department. The ArcGIS Platform is an integrated web-GIS system that provides a wide range of capabilities for storing, managing, analysing, visualising and sharing geospatial data for all users within the organisation. The Platform provides the framework of data and technology needed to address a wide range of location-related business processes. Through change management processes, the department utilised ArcGIS Platform to introduce a method of reporting incidents at schools, backed up by photographic evidence.

survey123 — *Integrated mobile component of the School Early Warning System*

The implementation of the School Early Warning System through ArcGIS Platform, support the Programmes of the Department’s Strategic Plan Document, the Annual Performance Plan and Medium-Term Framework Plan which are in a form of Five Year Plan and are identified as indicators within the following Strategic Objectives:

Ensure effective governance processes
Improved functionality and performance of schools
Enhanced accessibility of special schools
Accessible quality Grade R Education
Infrastructure management in schools and
Examination services managed

As part of the solution, the incidents will be loaded and locked in a centralised server via mobile device (Survey 123) wherein a unique identifier will be allocated to the incident for tracking purposes.

The Department Official will acknowledge receipt of the incident to update its status to received or in progress, in an Operations Dashboard.

The school will have access to track the status of the incident logged via a Dashboard

By understanding the main objectives of the North-West Department of Education and Sport Development to support the various schools and functions, the optimal implementation of the ArcGIS Platform serves as the right solution to meet the challenges faced by Department.

Demystifying Web GIS

August 2, 2017 richard@esriLeave a comment

what is webgis

GIS is evolving. That is a fact, but equally true is how quickly this is happening. Sometimes just keeping up with it all seems overwhelming. So how can we simplify some of these new concepts such as “Web GIS” and the “Web AppBuilder”? And once you know the potential of modern Web GIS, how can you be successful in leveraging that within your organisation? Esri South Africa hosted a seminar on 28 July to unpack these topics and show some examples of how Portal for ArcGIS can be used and configured to suit the way your company operates.

In summary, Web GIS is very much the GIS we already know and love. It is now just much more accessible using web technologies and is greatly simplified/configurable to suit the wider audience it now caters to. Look through a copy of the presentation from the seminar to get an idea of what was discussed and feel free to leave a note, comment, thought or problem in the comments below.

Demysitfying Web GIS – Esri South Africa Seminar – July 28

Happy web gis’ing!

– Richard

Esri and the 3rd dimension

June 28, 2017June 28, 2017 carlbesterLeave a comment

With Esri’s ever expanding software stack it is sometimes difficult to keep track of the variety of software solutions available. One of the main areas of growth is Esri’s collection is its answer to 3D GIS. Fully utilising the extra dimension has come difficult to the GIS sector in the past (which is historically mostly two-dimensional in terms of application). Esri’s recent focus on developing a 3D stack which fully embraces three-dimensional analysis, content generation and visualisation with the emphasis on sharing 3D scenes with non-technical users has led to mainly two desktop applications, ArcGIS Pro and CityEngine. This blog post will have a look at both of these applications by discussing the capabilities and when to use them through a typical use-case for an area around central Johannesburg.

ArcGIS Pro:

ArcGISPro

ArcGIS Pro allows users to seamlessly integrate traditional two-dimensional GIS with 3D data in a single application interface. Using the 3D Analyst extension a user can perform various 3D analysis on GIS data including line of sight, volumetric calculations, viewshed calculations as well as working with LAS datasets, as well as the traditional GIS analysis methods like proximity, overlay and statistical analysis. For more information regarding the 3D Analyst extension visit: http://www.esri.com/software/arcgis/extensions/3danalyst.

The image below shows a Johannesburg scene showing 3D textured buildings, analytical representation of trees and extruded polygons showing the various zones and height restrictions of the buildings. This gives the user the ability to quickly see which building exceed their height restrictions.

ArcGISPro001 — Overlay 3D buildings and zonal restrictions in ArcGIS Pro

Next we need to calculate how the shadows in the city change over course of a specific day, and share the result with external users.

Use the Sun Shadow Volume geoprocessing tool (3D Analyst) to calculate the shadow volumes. In the example below the analysis were done between 08:00 and 16:00 for every two hours.

The resulting multipatch represents the shadow volumes created by each building at a specific time. ArcGIS Pro has the ability to cycle through these time-enabled data to create a seamless animation of the shadow movement.

Webp.net-gifmaker (1) — Shadow movement over the course of the day

Share the scene to either ArcGIS Online or Portal with ease. An example web scene for of the shadow analysis mentioned above can be viewed here.

*The next blog post will focus on the various 3D sharing techniques available in the ArcGIS Platform

ArcGIS Pro is a powerful tool for performing 3 dimensional analysis on GIS data. However, although ArcGIS Pro has 3D editing capabilities, its primary function is not 3D content creation. CityEngine on the other hand was designed especially for quick content generation on a large scale.

CityEngine:

CityEngine’s ability to dynamically create and compare urban scenarios quickly makes it a favourite among urban developers, local governmental authorities, township planners as well as the entertainment industry.

The key behind CityEngine’s quick content generation is its own procedural scripting language called CGA. These scripts or rules are basically a set of sequential tasks that guides the software to create accurate 3D geometries.

By applying different rules to the same datasets, we are able to generate various 3D representations. In the example below, we can see that in the larger view a more realistic scenario is generated displaying textured buildings and highly detailed trees. The inserted image shows the same datasets represented differently to produce a more analytical scenario of the data.

2017-06-27 08-05-47 AM — Using CGA rules creates multiple scenarios quickly using the same data

In another example, an urban designer might want to compare scenarios for a redevelopment project. In the image below CityEngine is used to compare high rising buildings, office spaces and apartment building designs.

Webp.net-gifmaker — Comparing redevelopment strategies in CityEngine

A CityEninge scene can be easily shared in a variety of ways. These include:

A CityEngine webscene is a static version of the CityEngine scene. All models, terrains and networks generated in CityEngine is compressed into a single .3ws file. This file can then be added as an item in ArcGIS Online or Portal, and when opened creates a browser based 3D environment that allows user-driven navigation and interaction. An example of the CityEngine web scene can be found here.

Comparing Real world and Analytical representations

Compare redevelopment scenarios

Add HTML embedded attributes

The image above shows examples of:

comparing real-world and analytical scenes (top left)
comparing redevelopment scenarios (top right)
adding HTML embedded attributes such as Google Streetview (bottom)

Datasets can also be exported to a Scene layer package. A Scene layer package has the ability to publish hosted scene layers which represents 3D data as a feature service, when added to either ArcGIS Online or Portal.

CityEngine also has the ability to share a scene as a 360 Virtual Reality experience. This creates a .3vr file which can be shared to ArcGIS online. Using a Samsung Gear VR headset along with the ArcGIS 360 VR app from Esri Labs, you are able to explore scenes in a fully immersive 3D virtual reality.

Find the Johannesburg 360 virtual reality scene here.

For more information about creating a 360 VR experience in CityEngine go to the Esri CityEngine Help.

Projection, Georeferencing and Spatial Adjustment CAD

June 8, 2017June 8, 2017 Melikhaya SihawuLeave a comment

Projection

A map projection is a method for taking the curved surface of the Earth (3D) and displaying it on a flat surface (2D). A projected coordinate system is always based on a geographic coordinate system. The below table shows a few key differences between a GCS and PCS.

GCS (Geographic Coordinate System)	PCS (Projected Coordinate System)
3D Spheroid Surface	2D Flat Surface
Latitude and Longitude	XY Locations
Datum	Map Projection

Map projections are designed for specific purposes. Conformal projections preserve the shape of the features, Equal area projections preserve the area of the feature displayed, Equidistant projections preserve the distance between certain features on a map while the Azimuthal projection maintains the directions of all points on the map.

Common Errors Due to Incorrectly set Coordinate Systems

Quick Easy Steps for Projecting

Enquire with the source owner of the data, research or decide which coordinate system the data should be assigned. If the original coordinate system of the data cannot be sourced, it will be your responsibility to assign the correct coordinate system to the data.
Before deciding which coordinate system the data should be assigned; visually assess the data or the layer properties of the data, to check whether the data is originally in GCS (Geographic Coordinate System) or PCS (Projected Coordinate System). Add the data in the Map Window in ArcMap.
Take note of the Extent that has large numbers 361332,327979dd. This indicates that this is a Projected Coordinate System.

Notice the Extent has small numbers -26,333041?? starting with to decimals. This indicates that they are Decimal Degree measurement which is a Geographic Coordinate System
Define the coordinate of your data by using the Define Projection tool (This tool is for datasets that have an unknown or undefined coordinate system defined)
After defining the coordinate system of the data, check against a Basemap if it is located at the correct place.
Project the data using the Projection Tool (This tool is to change the dataset from one coordinate system to another)

Georeferencing and Spatial Adjustment

Georeferencing

Provides a correct, real-world spatial reference to Raster or CAD datasets; which is either missing a real-world spatial reference or has an unknown spatial reference.

Georeferencing is the process of aligning geographic data to a reference dataset in a known coordinate system. This method helps to associate a physical map, raster or CAD document with a spatial location. When you Georeferencing a dataset, you define where the data is located using map coordinates. Georeferencing uses Control Points, that associates the data with a specific location on earth; which allow the georeferenced dataset to be viewed, queried and analysed with other geographic data.

During Georeferencing it is important to use correct Reference Datasets; raster or vector feature classes can be used as reference data only if the data has the correct spatial reference. Identify distinctive locations that are visible in both datasets, these will be used as Control Points. The control points link the original dataset that is being georeferenced to the reference data – the first control point is plotted on the original dataset (data that needs to be aligned with the reference data) the second control point is then plotted on the corresponding location on the reference data. Corresponding Links are established from the control points, which will be used to align the original dataset with the reference data.

Spatial Adjustment

Like Georeferencing; Spatial Adjustment aligns the original dataset to a reference data, based on links between corresponding control points. The major difference between the two methods is the original datasets and the usage of the method; Georeferencing is used to re-create a missing or unknown spatial reference for Raster or CAD data while Spatial Adjustment is used to correct the alignment of editable vector data.

Data in GIS usually comes from different sources, which means the user is required to perform additional work to integrate and use the data together. Spatial adjustment is used to correct; inconsistencies between data sources, correct geometric distortions and align features together. There are a variety of adjustment methods that can be used to adjust all editable data sources. Another interesting task in spatial adjustment is the ability to transfer attributes from one feature to another.

There are three methods for performing spatial adjustment: transformation, edgematching and rubber sheeting. The edgematching method is typically used for connecting the end points of features with each other, rubber sheeting is best used for aligning minor geometric adjustments; this method stretches, shrinks and reorients features to match the reference data and the transformation method is like the transformation method used in georeferencing; it will shift, scale, rotate and skew the data if necessary.

The table below shows the major differences between the two methods above.

Georeferencing	Spatial Adjustment
The process of aligning data with missing or unknown spatial reference to reference data in a known coordinate system	Editing functionality for aligning data with a spatially accurate reference dataset
Transformation Method	Transformation Method Edgematching Method Rubber Sheeting Method
Works Out of the Edit session	Works in the Edit Session
CAD, Raster Imagery, Aerial Imagery	Feature Class or Shapefile (editable vector data)

Common Errors Due to Inconsistency in Data

georef_cad — Error showing an un-georeferenced CAD Layer

inconsitency — Errors showing Features Classes (vector data) that do not align to the Reference Data

Quick Easy Steps for Correctly Aligning CAD/DWG Data

Assign GCS (Geographic Coordinate System) to the CAD/DWG file (WGS_1984) in ArcCatalog, if it has no spatial coordinate system / unknown coordinate system.
Load a Basemap for reference purposes, it is advisable to choose the South Africa Cadastre Basemap available on ArcGIS Online Basemap especially if you are using CAD/DWG Files.
Georeference the CAD/DWG file, using the reference data (data in the correct geographic location that has the correct Spatial Reference i.e. farm portions).
When Georeferencing; it is vital to have two distinctive locations in both the CAD/DWG File and the Reference Data, these two distinctive locations will be used as Control Points.
Export the georeferenced CAD Feature to a Feature Class place it in a file geodatabase once georeferenced, first create a new file geodatabase if necessary. Working with Feature Classes is recommended especially if you must spatially adjust the data after Georeferencing.
Adjust the feature class by using Spatial Adjustment (use the Affine method)
Use the Define Projection tool to define a coordinate for the feature class that perfectly aligns with the Reference data.
Project, it accordingly and assess the results

Limitations of Georeferencing CAD datasets

Georeferencing a CAD dataset is limited to one- and two-point transformations using the similarity transformation method:

one-point transformation comprises one link and moves the dataset
two-point transformation comprises two links and moves, rotates, and scales the dataset uniformly

Both methods preserve the shape and angles of the CAD dataset, however, the aspect ratio (the ratio of the width to the height of an image or screen) of the CAD drawing is distorted

Spatial Adjustment of CAD datasets

The spatial adjustment method maintains the aspect ratio of the CAD drawing and prevents skewing to the x- and y- axes. However, it should be noted there will be an inherent deformation of the aspect ratio, from the georeferencing step.

Contributor: Busisiwe Ngobe

Understanding Survey Diagrams

June 8, 2017June 8, 2017 Melikhaya Sihawu1 Comment

Surveying is all about measuring distances, angles and positions on or near the surface of the earth. Surveyors use mathematical techniques to analyse field data. Survey measurement relies on understanding two basic scientific, accuracy and reliability.

Types

Plane surveying: Earth surface is considered a 2D plane with x-y dimensions.
Geodetic surveying: Earth surface is considered spherical (ellipsoid) 3 dimensional

Classes

Preliminary survey (data gathering): is the gathering of data (distances, position and angles) to locate physical features (rivers, roads and other structures) so that data can be plotted to scale on a map or plan, also include the difference in elevation so that contour could be plotted.
Layout survey: Marking on the ground (using sticks, iron bar or concrete monuments) the features shown on a design plan features: – Property lines (subdivision survey). – Engineering work (construction survey). – Z-dimensions are given for x-y directions.
Control survey: used to reference preliminary and layout surveys.

Horizontal control: arbitrary line tied to the property line or HWY centre or coordinated control stations.
Vertical control: Benchmarks: points whose elevation above sea level is defined accurately.

Different methods of surveying

Topographic survey: preliminary surveys used to tie earth surface features.
Hydrographic survey: preliminary surveys tie underwater feature to surface control line
Route surveys: preliminary, layout and control surveys that range over a narrow but long strip of land (highways, railroads, electricity transmission lines and channels).
Aerial survey: preliminary and final surveys to convert an aerial photograph into scale map using photogrammetric techniques.
Construction survey: layout of engineering work.
Built survey: preliminary surveys tie in features that just have been constructed
Property surveys: preliminary, layout and control surveys determine boundary locations.

Unit of measurement

There are two main measuring systems:

English system and Metric system (SI units).

Angles are measured by: Degrees, minutes and seconds.
1 revolution = 360 degrees, 1 degree = 60 minutes and 1 minutes = 60 seconds

http://faculty.kfupm.edu.sa/CE/hawahab/WEBPAGE/CE260/NOTES/1CE260%20CH%20%201.pdf

Types of survey diagram

Servitude diagrams (powerlines, pipelines or municipal services) for registering servitudes over an existing property.
Lease diagrams for registering long leases over portions of properties.
Consolidation diagrams when it is required to consolidate several individual properties into one, taking out certificates of consolidated title.
Mineral diagrams to register mineral rights separately from the land rights.
Mining title diagrams for registering the right to extract minerals from the land.

http://csg.dla.gov.za/diagram.htm

Coordinate systems

SA_Coordinate

Angles of direction

Directions are measured clockwise which is the opposite for GIS data (counter clockwise).

Azimuths

Azimuths are horizontal angles measured clockwise from any reference meridian.
In a plane surveying, azimuths are generally measured from north/south starting at 0⁰.
Azimuths are used advantageously in the boundary, topographic, control and other kinds of survey, as well as in computations.

In the south azimuth system, the angles are measured clockwise from south 0⁰.

south azimuth system

ArcGIS by default, accept angular measurements of the polar direction measuring system

Polar angles are measured counter-clockwise from the positive x-axis, east 0⁰.

c_clockwise

Bearing

Assumes that total station is set up at points A, B, C, D, E, F and G; bearing read on lines AB, BC, CD, DE, EF and FG.
AB, BC, CD, DE, EF and FG are forward bearings and the inverse will give backwards bearings
Both the forward and backwards bearing should have the same numerical values.

One can change the direction measuring system and angular units the editing tools use on the Units tab of the Editing Options dialog box.

http://moodle.najah.edu/pluginfile.php/47169/mod_resource/content/0/Angles_Azimuths_Bearings.pdf

http://desktop.arcgis.com/en/arcmap/10.3/manage-data/editing-fundamentals/about-direction-measuring-systems-and-units.htm

Contributor: Lutho Mbeki

5 Reasons to attend the Esri South Africa Business Summit 2017

April 6, 2017April 6, 2017 Lebogang Mashishi2 Comments

BusinessSummit

Have you heard? Esri South Africa is hosting its first ever Business Summit on the 5^th of May 2017 in Midrand, Johannesburg.

The main aim of the event is to bring together industry experts, potential GIS users and implementers, Esri SA visionaries for an interactive experience to exchange proven practices and gain actionable intelligence.

This event is the ideal setting for you to gain insights into industry trends and opportunities, realize the greatest value from your GIS technology investment and map GIS into your go-to market strategy for growth.

So as we are getting ready for the 2017 Esri SA Business Summit, we would like to share with you some reasons we think you should join us

Network and build business relationships.

Discover industry best practices from the best in the business.

Gain valuable Industry knowledge, tips and tricks from other GIS implementer’s in the commercial space.

Spend one-on-one time with Esri SA’s professionals and specialists. You will get a chance to talk about opportunities and business needs with our sales team.

Cocktails!

I hope to you see you there 😊

If you are in interested in attending the summit or would like to send a query, please feel free to contact our marketing team: marketing@esri-southafrica.com

Broadband in South Africa

April 4, 2017 clintonLeave a comment

Broadband in South Africa

Whether it is mobile or fixed broadband services, consumers are demanding cheaper and faster speeds. Consumers have become brand agnostic and have become data hungry.

How do you differentiate yourself from your customer? Better services, faster speeds and rapid deployment of broadband services. This requires huge capital expenditure and exploring unknown markets.

Esri South Africa have helped our customers in the rapid build and design of their networks using the ArcGIS Platform. Using mobile applications our customers can update, capture and report on their network. This has changed the way in which our clients operate; instead of using paper based maps, our clients are enabled to manage their network from the field. With the introduction of BYOD, it helps organizations reduce hardware expenses.

Our mobile applications have enabled our clients to engage directly with the client by means of integrating CRM’s and allows the rapid deployment of their sales force into the field.

Esri helps you answer the question of “where” and solve problems. You transform your telecommunication company provide better service via your network assurance team, plan and build team and sales team. Esri provides a complete system that allows you to integrate disparate data, access and update information from the office or the field, and maintain a real-time view of all operations. More than maps and applications, Esri gives you the location analytics you need to save time, lower costs, and satisfy customers.

Powered by ArcGIS – An OMS solution deployed in less than a week!

February 14, 2017February 16, 2017 roger@esriLeave a comment

arcgis-for-electric-esri-sa

What do potholes and electric outages have in common? Like puncturing a tyre when hitting an unexpected pothole, power disruptions can cause emotional and economic havoc. Most South Africans can recall the power crisis of 2015 which disrupted many lives and caused damage to the economy. For most, the power cuts were unexpected and often lead to financial consequences such as replacing damaged home appliances, or psychological effects such as missing their favourite prime time TV show.

Our customers in the Electric utilities industry have realised the value and benefits of improving their Outage Management System to better serve the economy and community at large. By implementing the ArcGIS platform, electric utilities are managing outages by integrating systems and geo-enabling both employees and the public through the power of location.

The utility’s GIS is usually the source of the network model whereby advanced location analytics enables smarter outage predictions and mapping. Eskom is an example of a customer who has embraced the use and benefits of the ArcGIS platform to visualise outages on their electrical network.

In an article published in the November 2016 issue of the PositionIT magazine, Gerhard Brits, Keagen Liebenberg and Shaun Goodbrand from Eskom explained how they leveraged the ArcGIS platform to create a national 2016 voting station outage web mapping application in only 5 days. By consuming information form two separate systems for multiple and single customer outages (FMS and CC&I) the team created links between reported faults and the 22 614 voting stations which allowed them to visualise which voting stations were experiencing outages. ArcGIS for Server was used to host and publish data exposed by desktop and web clients. Portal of ArcGIS was used to control access to the platform and Web AppBuilder for ArcGIS was used to create application-specific tools.

eskom_platform

“The combination of these software utilities provides a very agile environment that allows the team to respond to user requirements in a timely manner” – Gerhard Brits.

For more information on this project, see http://www.ee.co.za/article/national-2016-voting-station-outage-map.html#.WHjjI8vRbqA

Esri helps you answer the question of “where” and solve real world problems. You transform your utility operations when you can quickly query, analyse, and understand your data. Esri provides a complete system that allows you to integrate disparate data, access and update information from the office or the field, and maintain a real-time view of all operations. More than maps and applications, Esri gives you the location analytics you need to save time, lower costs, and satisfy customers.

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