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2 and 3 dimensions capturing processing and analysing 2d and 3d data 2 and 3 dimensions capturing processing and analysing 2d and 3d data menu skip to content home about near global coverage of 1 arc second srtm is becoming available november 25 2014 by ralf hesse the near global srtm digital elevation model has been an extremely valuable data set for many years now that data set has a resolution of 3 arc seconds equalling roughly 90 m a higher resolution 1 arc second or approximately 30 m had been availbale for the usa and higher resolution data had been available for small areas for many years researchers around the world have been hoping and waiting for a higher resolution near global or dem to become available the aster global dem with a nominal resolution of 30 m is great because it does offer global coverage in contrast to the srtm dem which does not cover regions north of 60 north and south of 58 south however the aster dem suffers from data artefacts and quality assessment showed that despite a pixel size of 30 m the effective spatial resultion is only approximately 120 m in late 2012 i was told at a conference that a 1 arc second srtm dem was forthcoming within a year or two now nasa has begun to release the near global i e limited to between 60 north and 58 south 1 arc second approximately 30 m srtm data set at least africa europe and south america are now available through the usgs s earth explorer already at first glance this new data set is in moast areas far superior to both the 3 arc second srtm dem and the aster global dem of course as in the 3 arc second srtm dem desert sand dunes at least in hyperarid deserts are recorded poorly because such surfaces simply did not backscatter enough of the radar signal no data areas in the 1 arc second strm dem are even slightly larger than in the 3 arc second srtm dem the aster dem still is the superior data set for such surfaces 3 arc seond srtm dem shaded relief image of the dunas pamps blanca palpa region note extensive data gaps in the dune field aster global dem aster gdem is a product of meti and nasa note good representation of the dune field and intense elevation noise on flat terrain in the northwestern portion of the image 1 arc second srtm dem note extensive data gaps in the dune field and good representation of flat terrain in northwestern portion of the image to assess elevation accuracy i compared the 1 arc second srtm dem with the state wide high resolution lidar based dem of germany s federal state baden württemberg 35 752 sq km or 56 4 million srtm 1 arcsec data pixels that data set has a reolution of 1 m so it had to be resampled to match the 1 arc seond resolution of the new srtm data i used both the dtm digital terrain model bare earth model and dsm digital surface model including vegetation and also looked at land use types forest agricultural land and grassland shaded relief images of a small subset of baden württemberg comparing lidar based dtm and dsm both resampled to 1 arc second with srtm 1 arc second dem lidar data c landesamt für geoinformation und landentwicklung baden württemberg elevation difference between srtm 1 arc second dem and lidar based dtm on average the srtm dem is approximately 1 m too low in baden württemberg comparison between different land use types clearly illustrates that the radar based srtm dem records vegetation canopy rather than ground surface this is also but less clearly visible in the shaded relief images these images also show that the lidar based dsm has an overall clearer appearance and shows more detail effective spatial resolution of the 1 arc second srtm dem does therefore not equal 1 arc second elevation difference between srtm 1 arc second dem and lidar based dsm for open land grid cells open land grid cells here defined as those for which the difference between lidar dsm and dtm is less than 0 5 m absolute difference between lidar based dem and srtm 1 arc second because the srtm dem corresponds roughly to vegetation canopy its apparent accuracy in forested areas is relatively low when compared with a lidar based dtm e g 10 of all srtm grid cell elevations differ more than 15 m from the lidar dtm however when looking at open land grid cells only i e those grid cells where the difference between lidar dsm and dtm is very low almost two thirds of all srtm grid cell elevations are within 2 m and more than 90 are within 7 m of the lidar dsm elevations all in all the new srtm dem is a big step forward in the field of near global elevation data sets posted in digital elevation remote sensing srtm tagged digital elevation remote sensing srtm leave a comment post navigation older posts search recent posts near global coverage of 1 arc second srtm is becoming available structure from motion tips and tricks dem visualisation techniques openness working with livt file size limits and performance rotation is the enemy archives november 2014 february 2014 january 2014 december 2013 june 2013 may 2013 november 2012 categories archaeology conference digital elevation lidar photogrammetry pole aerial photography remote sensing software srtm structure from motion uav uncategorized visualisation workshop meta create account log in entries feed comments feed wordpress com blog at wordpress com 2 and 3 dimensions create a free website or blog at wordpress com subscribe subscribed 2 and 3 dimensions sign me up already have a wordpress com account log in now privacy 2 and 3 dimensions subscribe subscribed sign up log in report this content view site in reader manage subscriptions collapse this bar loading comments write a comment email required name required website design a site like this with wordpress com get started