Elevation

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ELEVATION

The database includes a global digital elevation model (DEM) developed from the Shutter Radar Topography Mission(SRTM) data (for more information on the data source, see links). There is a high resolution (srtm3) and low resolution (srtm30) dataset available in the database. The function elevation.srtm_getvalue extracts the land surface elevation (m) stored in the database for a given set of coordinates (longitude and latitude) which is parsed as text in the function. The elevation.srtm_getvalue function will first try the high-resolution dataset for the specific location and the low-resolution if the first did not give a result.

 The function can be used in different ways, shown below.


Usage

 select elevation.srtm_getvalue(ST_pointfromtext('POINT(<longitude> <latitude>)',4326))

i.e.


 select elevation.srtm_getvalue(ST_pointfromtext('POINT(6.99666 49.504)',4326))
  
 or
  
 select elevation.srtm_getvalue (ST_pointfromtext('POINT(86.93333 27.983333)',4326));


To use only high- or low resolution the following can be used resp.

 select elevation.srtm3_getvalue(ST_pointfromtext('POINT(6.99666 49.504)',4326)) -- high res
 select elevation.srtm30_getvalue(ST_pointfromtext('POINT(6.99666 49.504)',4326)) -- low res


If a user would like to access the elevation data for a series of locations, than the location field can be used, which is a composite, text field including longitude and latitude of each GPS point, do not run this query for very large datasets without testing first on a subset of data.

 SELECT device_info_serial, date_time, latitude, longitude, elevation.srtm_getvalue("location") AS DEM
 FROM gps.ee_tracking_speed_limited 
 WHERE device_info_serial = <device_info_serial> 

i.e.


 SELECT device_info_serial, date_time, latitude, longitude, elevation.srtm_getvalue("location") AS DEM
 FROM gps.ee_tracking_speed_limited
 WHERE device_info_serial = 60
  
 

On borders between cells the south and/or east cell is selected, also between tiles!


Notes :


The 27 tiles for srtm30 are placed in one table. The 900 tiles from srtm3 are classified according to the srtm30 classification and distributed to 27 tables.

All tiles have been redistributed into rasters of 60 * 60

Usage within R

If a user would like to access the elevation data for a series of locations, than the location field can be used, which is a composite, text field including longitude and latitude of each GPS point, do not run this query for very large datasets without testing first on a subset of data. This function can also be used from with R but needs a slightly different notation (namely removing quotations around the field location). In the following query elevation.srtm_getvalue(location) AS DEM returns the surface elevation (m) and altitude - elevation.srtm_getvalue(location) AS ALT_AGL returns the GPS altitude above the surface (m) for one specific bird and within a range of dates:

 SELECT device_info_serial, date_time, latitude, longitude, elevation.srtm_getvalue(location) AS DEM, altitude - elevation.srtm_getvalue(location) AS ALT_AGL
 FROM gps.ee_tracking_speed_limited 
 WHERE device_info_serial = <device_info_serial> and date_time >= 'yyyy-mm-dd hh:mm:ss' and date_time <= 'yyyy-mm-dd hh:mm:ss'

i.e.

 SELECT device_info_serial, date_time, latitude, longitude, elevation.srtm_getvalue(location) AS DEM, altitude - elevation.srtm_getvalue(location) AS ALT_AGL
 FROM gps.ee_tracking_speed_limited 
 WHERE device_info_serial = 6015 and date_time >= '2014-06-27 00:00:00' and date_time <= '2014-06-28 00:00:00'

Links

Credits

This postgresql adaptation of the SRTM3 v3 is made by F.P. Sluiter. The original 6000*6000 tiles are retiled to 60*60. New tiles containing only no_data values were removed. Dataset is subdivided in 27 tables that cover the globe.

april 2008, University of Amsterdam

Please put the following reference in publications:

"F.P. Sluiter, University of Amsterdam, april 2008, SRTM3 postgresql adaptation ; based on Jarvis A., H.I. Reuter, A. Nelson, E. Guevara, 2006, Hole-filled seamless SRTM data V3, International Centre for Tropical Agriculture (CIAT), available from http://srtm.csi.cgiar.org."

Original documentation: PROCESSED SRTM DATA VERSION 3

The data distributed here are in ARC GRID, ARC ASCII and Geotiff format, in decimal degrees and datum WGS84. They are derived from the USGS/NASA SRTM data. CIAT have processed this data to provide seamless continuous topography surfaces. Areas with regions of no data in the original SRTM data have been filled in using interpolation methods. A full technical report on this method is in preparation.


DISTRIBUTION

Users are prohibited from any commercial, non-free resale, or redistribution without explicit written permission from CIAT. Users should acknowledge CIAT as the source used in the creation of any reports, publications, new data sets, derived products, or services resulting from the use of this data set. CIAT also request reprints of any publications and notification of any redistributing efforts.

NO WARRANTY OR LIABILITY

CIAT provides these data without any warranty of any kind whatsoever, either express or implied, including warranties of merchantability and fitness for a particular purpose. CIAT shall not be liable for incidental, consequential, or special damages arising out of the use of any data.

ACKNOWLEDGMENT AND CITATION

We kindly ask any users to cite this data in any published material produced using this data, and if possible link web pages to the CIAT SRTM website (http://srtm.csi.cgiar.org).

Citations should be made as follows:

Jarvis A., H.I. Reuter, A. Nelson, E. Guevara, 2006, Hole-filled seamless SRTM data V3, International Centre for Tropical Agriculture (CIAT), available from http://srtm.csi.cgiar.org.

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