Request for changes-115: Refactoring of DownloadSRTMTiles

[Request for Changes - 115] Refactoring of DownloadSRTMTiles

Status

• Author: Guillaume
• Additional Contributors (if different than authors)
• Submitted on 08.09.2017
• Proposed target release: 6.2
• Adopted : +3 Julien, Victor, Rémi
• Merged : 2f51a92981c11e2e8e63f6c6dd3b1bde0bcf32ce

Summary

This RFC is a refactoring of the application DownloadSRTMTiles.

Rationale

Following discussions during last OTB Users Days, issues have been raised about this application : no support of SSL in OTB packages, application unable to check tiles already downloaded and tiles not available in SRTM.

Implementation details

Applications

M       Modules/Applications/AppImageUtils/app/otbDownloadSRTMTiles.cxx

Here is a description of the main changes in the application:

• there is a single parameter for tile directory : "tiledir" ("mode.download.outdir" and "mode.list.indir" has been removed)
• there is a default list of SRTM tiles hard-coded in the application. It is used to check SRTM / nonSRTM tiles. The storage structure for tile identifier is lightweight (memory size for the whole SRTM list : between 35kB and 42kB).
• reports have been changed, the application now gives the number of : nonSRTM tiles, local tiles and tiles to be downloaded. In "list" mode, the status of each tile is returned in the logs.
• For the moment, the coverage ratio is only computed based on the ratio of SRTM tiles over the total number of tiles covered.
• there are several ways to define the requested area (they can be used simultaneously):
  • an image list
  • a vector data list
  • a list of tile names

An example of output with 'list' mode:

bin/otbcli_DownloadSRTMTiles -il ../../src/OTB-Data/Examples/QB_Toulouse_Ortho_PAN.tif -vl ../../src/OTB-Data/Input/waterways.shp -names N67E001 -tiledir ../../src/OTB-Data/Input/DEM/srtm_directory -mode list
2017-09-08 11:35:19 (INFO): Total candidate tiles: 16
2017-09-08 11:35:19 (INFO):   --> 1 missing tiles in SRTM (coverage ratio is 93%)
2017-09-08 11:35:19 (INFO):   --> 2 tiles already in the directory
2017-09-08 11:35:19 (INFO):   --> 13 tiles to download
2017-09-08 11:35:19 (INFO): Status of each tile (NotSRTM/Local/Missing):
  N67E001 = NotSRTM
  N43E001 = Local
  N44E003 = Local
  N42W001 = Missing
  N42E000 = Missing
  N42E001 = Missing
  N42E002 = Missing
  N42E003 = Missing
  N43W001 = Missing
  N43E000 = Missing
  N43E002 = Missing
  N43E003 = Missing
  N44W001 = Missing
  N44E000 = Missing
  N44E001 = Missing
  N44E002 = Missing

Tests

M       Modules/Applications/AppImageUtils/test/CMakeLists.txt

Test updated with new parameter names.

SuperBuild & Packaging

M       SuperBuild/CMake/External_curl.cmake
M       SuperBuild/CMake/External_openssl.cmake

In order to download tiles from the SRTM server, cURL has to have HTTPS support. For that, the following choice has been made in SuperBuild:

• On Linux : we compile OpenSSL, and build cURL using OpenSSL.
• On Mac and Windows : cURL doesn't use OpenSSL, but the native SSL implementation
• In order to do that, cURL has been upgraded to 7.54.1