I have an Orthomosaic and a DEM (both are in Geotiff formats and have RGB values) of a site, and I want to check their accuracy. For this purpose, I measured the 3D location (with mm accuracy) of some fixed features on-site with a total station. For accuracy comparison, I need the 3D coordinates of those fixed features from the orthomosaic (X,Y) and the DEM (Z).

I'm using ArcMap 10.1, and so far, the only way I could extract the above mentioned information is by placing the cursor on each feature and manually read the (X,Y) coordinates from status bar.

I have over 400 features to compare and manual reading of the coordinates takes a lot of time.

1) Is there a way that I could use click and save (or similar automated procedure) to obtain the (X, Y) coordinates from orthomosaic.

2) Also, I want to extract the Z coordinates from the DEM for a set of (X,Y) values. Is there an automated sampling procedure for this in ArcMap?

Note: I have the licenses for most 3D tools in ArcGIS including 3D analyst.

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as your orthomosaic is georeferenced, you can create a point feature layer, start an edit session and store each point when you click on it. After saving your edits, you can compute the X aand Y coordinates of eah point with the field calculator (calculate geometry). Then you can use "extract value to point" with the DEM file in order to get the Z value. Finally, add your reference point as a point event and join the attribute tables of the two sets of points using "spatial join" so that you can compute the RMSE.

  • Dear radouxju thanks a lot! hope you had a wonderful winter break. (X, Y) were really easy to get, however, unfortunately I do not have have a license for Spatial Analyst (extract values to point). I used qGIS to calculate Z values, however, when I try to join the (Z) shp file (or attribute table) from qGIS with the (X, Y) shp file (or attribute table) using FID, in arcmap, I get zero/null values. Am I doing something wrong? – asghar Dec 28 '16 at 20:27

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