topic Re: need help in georeferencing in Data Management Questions

need help in georeferencing

PolashBanerjee — Tue, 24 Mar 2015 17:47:26 GMT

I have a landuse map which doesn't have any coordinates. However, I have managed coordinates of around 8 control points in the form of small towns in the map. These points are well spaced from each other. Unfortunately, they are not placed in the corners of the map. Anyway my study area is very small (and most of the control points are close to my study area), as compared to the map, so I hope error percent will be low !!

which georeferencing method is appropriate to project this map? I am using ArcGIS 9.3.

Re: need help in georeferencing

JoeBorgione — Tue, 24 Mar 2015 19:14:55 GMT

What format is your landuse map? Is it a polygon feature class/ shapefile? An image?

You can look here for more details: ArcGIS Desktop Help 9.3 - Georeferencing toolbar

Re: need help in georeferencing

PolashBanerjee — Wed, 25 Mar 2015 15:52:10 GMT

its raster image.

Re: need help in georeferencing

JoeBorgione — Wed, 25 Mar 2015 15:56:46 GMT

You should be able to pick out some landmarks on the image like crossroads etc, and if you have data that supports those landmarks (like a street centerlines feature class of a known projection) you can then create your own control points.

There are several different methods (affine, etc) but I've never done anything but the default and its' always worked for me. Just follow the help file provided.

Re: need help in georeferencing

BenGrod — Wed, 25 Mar 2015 16:10:53 GMT

I second Joe's suggestion. Add imagery as a basemap to ArcMap, add the landuse map to be georeferenced, and use the Add Control Points tool on the georeferencing toolbar. After all of you control points are added and the landuse map is relatively where you would like it to be run the Rectify tool to output a new georeferenced landuse map with a defined coordinate system.

Re: need help in georeferencing

PolashBanerjee — Thu, 26 Mar 2015 17:40:38 GMT

Thankyou everyone. first I projected the image in the desired projection system and then I used landmarks as control points with known coordinates and updated them using georeferencing tool. it worked.