Archive for June, 2010

Using Excel to calculate the RMSE for LiDAR vertical ground control points



The height accuracy of the collected LiDAR data can be verified by comparing with independently surveyed ground control points on hard, flat, open surfaces. It is essentially just calculating the height differences for all the control points and then determining the height root mean squared error (RMSE) or differences. Most LiDAR processing software have the reporting function built-in. However, plain Microsoft Excel can also do the job (except for extracting the elevation from the LiDAR data).

Assuming that you are able to calculate the height differences for all the control points and place in a spreadsheet as shown in the figure below. I have a column of delta Z values in column A.

Then to calculate the RMS value for the elevation differences, I can do the following.

  1. In a cell, type in the formula:= SQRT(SUMSQ(A2:A18)/COUNTA(A2:A18))where A2:A18 are the values from cell A2 to A18 in the spreadsheet. Simply replace these with the actual locations on your spreadsheet.
  2. Press RETURN.
    The RMSE value is calculated.



Data acquisition: How do I know if this river is been well acquired?


I’ve already entered my river but my imagery was in 2D so… was it well acquired?…  First of all, I import my shape (shp) file into Global Mapper (what a great sofware!) and export my vector file as a KML.

Import my river.kml file into my brand new Google Earth 5.2 or just double-click it in his location… easyest impossible!.

Select it and use ‘show elevation profile’,  a very useful new tool for these purposes…

And that’s it, constant altitude, almost perfect!.

Hope you have considered it interesting:-)


The SketchUp 3D API: Working with 3D geospatial data


I hereby post this video by Matt Lowrie (Google). hope it’s interesting for you guys.


GIS+Architectural scenaries. Awesome!


Even from scratch or from dgn/dxf vectorial format’s contour lines you create your own scenario.

Then import your model previously created using Sketch-up (this time i used google’s 3d warehouse, thank you Dilbert).

Stamp your house using sketch-up sandbox tools.

Then fur your scenario as if it was grass…

A little of photoshop like clouds and thats it!

Alberto Concejal
geographer, 3d designer & 3D GIS technician
albertoconcejal [at]; My favorite route planner!


My very good friend Fernando (a spanish/english like friend of mine:-)) introduced me this magnificent route planner he was using at that moment (three years ago!!!!)… had a very interesting 3D engine, very easy to use and very reliable… I’ve been using it since but it has never been one of the most famous among route planners in the market…

I strongly recommend it and i really like it a lot! enjoy!

Alberto Concejal
geographer, 3d designer & 3D GIS technician
albertoconcejal [at]