Opened 12 years ago

Closed 12 years ago

Last modified 12 years ago

#4086 closed defect (fixed)

GCPs not read for Envisat MERIS reduced resolution scenes

Reported by: knutfrode Owned by: warmerdam
Priority: normal Milestone: 1.8.1
Component: GDAL_Raster Version: unspecified
Severity: normal Keywords: envisat, meris
Cc: antonio, knutfrode

Description (last modified by knutfrode)

Tested with GDAL versions 1.6 (Windows) and 1.8 (Linux), I find that GCP’s and coordinate systems (CS) are read for full resolution (MER_FR) scenes, but not for reduced resolution (MER_RR) scenes.

Here are the first output lines from gdalinfo for a reduced resolution (RR) scene:

Driver: ESAT/Envisat Image Format
Files: MER_RR__1PNRAL20100426_154828_000003662088_00498_42636_0001.N1
Size is 1121, 2081
Coordinate System is `'

For corresponding full resolution scenes, CS and GCP’s are reported before the Metadata. This example scene, and others, can be downloaded from

File structure for RR and FR scenes should be close to identical, so this probably requires a small fix only.


Change History (6)

comment:1 by antonio, 12 years ago

The method ScanForGCPs_MERIS relies on "LINES_PER_TIE_PT" and "SAMPLES_PER_TIE_PT" fields of the SPH, In MER_RR products such fields are not present.

Looking at sect values should be


comment:2 by warmerdam, 12 years ago

I have downloaded MER_FRS_1PNRAL20100426_091349_000000822088_00494_42632_0001.N1 and a gdalinfo report on it does not include any GCPs, geotransform or coordinate system information. I was hoping to establish a working baseline to compare the _RR_ sets to.

comment:3 by warmerdam, 12 years ago

Component: defaultGDAL_Raster
Status: newassigned

In fact, I do see these lines in MER_RR1PNRAL20100426_154828_000003662088_00498_42636_0001.N1.


Stepping through the code there seems to be a bunch of checking code for tie points per column based on the tiepoints per row logic. I have corrected this and now the MER_RR1PNR* dataset and the MER_FRS_1PN* dataset both have GCP sets.

The change is in trunk (r22403) and 1.8 (r22404).

Could someone do some additional testing of this?

Note, I also have a very small MER_RRBPNPDK20000620_103648_00000270A001_00180_00177_0642.N1 dataset that does not seem to have the LINES_PER_TIE_PT item or the corresponding tie point ADS. So apparently not all reduced resolution datasets will have GCPs.

comment:4 by knutfrode, 12 years ago

Description: modified (diff)

I have recompiled r22404, and can confirm that GCPs and coordinate systems are now read successfully for all the following tested scenes:


Prior to the update it worked only for the MER_FR-scene. I believe the ticket can be safely closed. Thanks a lot!

Note: the archive of sample MERIS-files has in the meantime moved to:

comment:5 by warmerdam, 12 years ago

Resolution: fixed
Status: assignedclosed

comment:6 by warmerdam, 12 years ago

Milestone: 1.8.1
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