Geo-referencing an aerial photo of Newton Park and overlay a vector layer HW Britz GISV431 & GEN 405

ArcGIS is a geographic-information-system (GIS) developed by ESRI. Being widely used and the sheer amount of functions and add-ons are maybe the important causes for being a big-player at universities as well. How to geo-reference a Aerial photo in ArcGIS? Objective To connect a scanned map or Aerial photo with other geographical data the map needs to be referenced. This means, that every pixel in the scanned image gets a new dimension: besides its location in the image (e.g. 326th pixel from left and 124th pixel from the top) it gets a real-world coordinate as well (e.g. 33°56′16”S and 25°33’11”E ). The objective of this tutorial is to show you how to translate these pixel-coordinates in real-world coordinates, aka. Georeferenciation Is (this even a word???)

OPEN ArcGIS

Now we need to adjust the visibility of the Geo-referencing Toolbar First open the Editor. There we choose Toolbar options ->Customize and a list with available toolbars will be opened. Now search for the Georeferencing and check it. The Toolbar shows up in your working window.

Define a projection In the first step we need to define a projection for the map: so the same term is also the function in ArcGIS: Define Projection

In the tool Define Projection we choose the scanned map as Input Dataset and the coordinate system that is defined in the description of the map

Zoom to your first Control Point.

Now create a point on this control point using the function Add Control Points. After marking the point use a right-click and choose the option “Input DMS of lon and lat” or if your CPs are in meters choose “Input X and Y”: a window will open. where you can record your pairs of input and output coordinates. Record the values that belongs to the latitude and longitude as DMS or Y- and X-value. Do this for the all of the CPs as well! if you don’t want to struggle with auto-projection use always opposing pairs (lower left, upper right, upper left, lower right).

As the transformation we will use 1st Order Polynomial (look here: Georeferencing- >Transformation. The result of the transformation needs to be exported using a right-click on the layer: Data->Export Data. It is important to give a name, file format and the storage place for the resulting raster in the Export Data dialogue.

In a new ArcMap document add the vector data you would like to overlay. Note that your coordinate System differs from your newly geo-referenced aerial photo

When you try to add the vector layer to your aerial photo the following massage appears: The Transformation will be done on the fly