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 An Oblique View of Terrain Mapping
Ryan Hamilton
Ryan Hamilton
Ryan Hamilton majored in Environmental Studies at the University of Colorado and has been employed within both the LiDAR and IFSAR mapping worlds since 1998. His interests (that all appear to be tied to mapping) include blue water sailing, backcountry skiing and big mountain and downhill mountain … More »

Why World 30?

November 7th, 2013 by Ryan Hamilton

NEXTMap® World 30™ has been an ambition of the Intermap® data engineers since the processing of the SRTM collection back in 2001. The lack of ground control for the SRTM dataset was an obvious area that could stand to be improved. Our radar engineers knew that when the right ground control became available a fantastic opportunity would present itself to update this detailed dataset and make it the best circum-world coverage dataset available. The secret ingredient was the introduction of NASA ICESat data. In raw form, this global set of LiDAR ground control points was a cumbersome mix of cloud strike points and anomalies. Intermap polished the raw ICESat data using an extensive filtering process that cleaned the data set and reduced it to 820 million ground control points, scattered with predictable regularity around the globe and boasting a vertical accuracy of 25cm RMSE or better. With this control data, an SRTM error mask could finally be created and applied to adjust the Z values of the SRTM DSM.

The second major problem facing users of the SRTM dealt with areas of voids and the missing coverage north of N60 degrees and south of S56. The ASTER data solved that one. Intermap used their proprietary data fusion technology and automated a ‘best match’ void fill to any null value throughout the now corrected SRTM. Where ASTER didn’t exist for an area, GTOPO30 was used. For the polar data the same ICESat correction was applied to the ASTER and again any voids were filled – this time with GTOPO30.

The end product is something we are very proud of. A global dataset with an absolute accuracy of +-7m.

If you are interested in more info on how NEXTMap World 30 was created, including the review of a new white paper detailing the use of World 30 in orthorectification, please join us for a special webinar jointly presented with Map Mart, Nov 14th, 2013 @ 11am PT; 1pm ET.  Click here to register:

Category: Oblique view of terrain data

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