Either deprecate ModelTypeGeocentric or provide an example

[max-martinez]

If there's a use case that justifies keeping this around, it should be illustrated.

[EmDevys]

I fully support this proposal, but I am wondering whether this should be deprecated or not. To the group, is there any identified use case of GeoTIFF using geocentric model? Or anybody having a connexion with Niles Ritter (who was JPL/NASA) or Mike Ruth (who was in SPOT image Corp) in order to get one example?

[EmDevys]

Use of GeoCentric is clarified in revised 1.1. Could anybody provide an example? (warmly welcome)

[EmDevys]

Even Rouault (email 29/05/2019) We had a discussion a couple months ago about if Geocentric CRS in GeoTIFF was something only theoretical or if there were actual use cases. Yesterday I just encountered such a case in https://github.com/OSGeo/gdal/pull/1596

What is interesting is that it is not for a "real" GeoTIFF file, but for a ASPRS LAS file which uses GeoTIFF encoding to encode SRS information, so there is no actual raster data.

[EmDevys]

Max Martinez (email 29/05/2019) That's a good find, but doesn't it actually suggest further support for deprecation of Geocentric in GeoTIFF? LAS 1.4 considers GeoTIFF descriptions of Coordinate Reference System information "legacy". WKT is now being used. And I don't think the earlier versions of LAS actually used GeoTIFF...they used the GeoKey tags.

[EmDevys]

Steve Olding (email 11/06/2019) From what I have seen so far, most of NASA's Earth-based GeoTIFF imagery is based on spherical/ellipsoidal geographical coordinate reference systems. In most cases, we are interested in locating artifacts relative to the Earth's surface or sea level. However, I understand that some of the Vesta (asteroid) imagery taken from the Dawn spacecraft uses a geocentric model. I imagine that this would also apply to Ceres but I have not yet confirmed.

Thinking about it, this seems to make sense. Earth can be reasonably accurately be descried by an ellipsoid and there are established geographical coordinate reference systems that allow us to georeference imagery to the Earth's surface. Things get a bit more complicated when we leave Earth and explore other objects in space that may not have established CRSs that we can use and may be sufficiently irregular in shape that they cannot easily be described by an ellipsoid.

https://trek.nasa.gov/vesta https://trek.nasa.gov/ceres https://solarsystem.nasa.gov/missions/dawn/overview/

I am trying to find out a bit more information but this would seem to suggest that it would be premature to deprecate the geocentric model type.

[EmDevys]

I also think that we can't deprecate any Geodetic model included in the GeoTIFF model in this minor revision, and this is the option which was decided in this revision (and stated by Roger Lott). Though this has been considered as "legacy" in LAS 1.4 (which unow uses WKT). However we still have to illustrate the specification by an example, either in the specification or a derived artefact. Some help wanted for such a geotiff geocentric example (there is a lunar projected example in F.3.4. Spherical Moon Example in the current document), but no geocentric example on the Earth nor any planet, satellite or asteroid).

[cmheazel]

If there is no example in GeoTIFF 1.0 and we plan to deprecate it in GeoTIFF 1.2, then why do we need an example? We could just add a note to 1.1 saying that due to lack of use the SWG plans to deprecate this GeoKey in future versions. If someone comes up with a requirement to retain ModelTypeGeocentric, then they can provide the example.

[EmDevys]

I am not sure it is reasonable to deprecate it in 1.1 (supposed to handle all models in GeoTIFF 1.0), even if it is mere deprecation. For not earth-related imagery, it seems quite a reasonable model fit - for purpose). It appears that the lunar example included in the specification is using a projected Model, but it could probably also have been under a geocentric model. NASA and probably other spatial agencies such as ESA or JAXA should have an interest. But in order to clarify that it is a real use case (and illustrate with an example), an example should be provided. Any volunteer for such an example?

[cmheazel]

@EmDevys I don't propose deprecation in 1.1. I propose notification of planned deprecation in 1.1. Deprecation would take place in 1.2 if there are no objections.

[cmheazel]

More to the point, why should we further delay this standard in order to provide an example for a GeoKey no-one seems to use?

[max-martinez]

OK, last several comments have confused me. Since I'm not going to be available on 6/26 thought I'd ask for clarification now to see just what everybody thinks "deprecate" means that it can't be done here. I generally have been assuming something in line with https://en.wikipedia.org/wiki/Deprecation. Does the OGC have a more specialized meaning? Note that deprecate in this definition neither means it is removed from the standard nor does it guarantee that it will be removed in the future. If we can come up with an example, great, though I'll also point out that this itself is a very low bar (just because something is doable doesn't mean that it needs to be standardized). I will note that the links that Steve Olding sent are showing lat,lon coordinates for both Vesta and Ceres, lol. I suspect if it is being used anywhere, my guess would be that it is with tie points only -- should still be fine, just show us! (Which now reminds me...should the spec actually allow people to use a RasterPixelIsArea raster space if they are only specifying tie points? I don't think it's disallowed but does it make sense? Food for later thought).

[cmheazel]

@max-martinez The Wikipedia definition is in-line with the way I have used deprecation before. It indicates a clause in the standard that has been used in the past but should not be used in the future. It is retained because implementations still exists in the wild and you need to know how to handle them.

[EmDevys]

Roger Lott (12/06) Geocentric coordinates underpin everything in modern geodesy. All other coordinates are derived from them. If GeoTIFF v2 ever comes to pass we will extend the list of (codes for) Model CRS types and geocentric will definitely be there. So it would be madness to deprecate it in v1.1. And I would say that to deprecate would be out of scope of the v1.1 revision. One of the reasons that examples are scarce may be that imagery is still in a 2D + 1D paradigm. I cannot see why retaining geocentric as a model CRS type must require an example: why? If it is only because no-one knows what they are then that is not an adequate reason.

[EmDevys]

Max, Steve, Roger I registered the following email content from Roger Lott under the issue #55 on github, for traceability :

I agree with Roger, but my opinion is that a nice Geocentric model example would illustrate those uncommon (though valid) elements, and allow to close the discussion.

For your other topic (should the spec actually allow people to use a RasterPixelIsArea raster space if they are only specifying tie points? I don't think it's disallowed but does it make sense?), as you are unable to participate to the SWG meeting on 26th June, I strongly recommend you to push it under issue #4, as we will also review open issues ahead of the meeting (and during the meeting as time allows), in order to finalize decisions on open issues.

Emmanuel

De : max-martinez [mailto:notifications@github.com] Envoyé : mardi 11 juin 2019 20:16 À : opengeospatial/geotiff Cc : Emmanuel Devys; Mention Objet : Re: [opengeospatial/geotiff] Either deprecate ModelTypeGeocentric or provide an example (#55)

OK, last several comments have confused me. Since I'm not going to be available on 6/26 thought I'd ask for clarification now to see just what everybody thinks "deprecate" means that it can't be done here. I generally have been assuming something in line with https://en.wikipedia.org/wiki/Deprecation. Does the OGC have a more specialized meaning? Note that deprecate in this definition neither means it is removed from the standard nor does it guarantee that it will be removed in the future. If we can come up with an example, great, though I'll also point out that this itself is a very low bar (just because something is doable doesn't mean that it needs to be standardized). I will note that the links that Steve Olding sent are showing lat,lon coordinates for both Vesta and Ceres, lol. I suspect if it is being used anywhere, my guess would be that it is with tie points only -- should still be fine, just show us! (Which now reminds me...should the spec actually allow people to use a RasterPixelIsArea raster space if they are only specifying tie points? I don't think it's disallowed but does it make sense? Food for later thought).

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[thareUSGS]

>> Geocentric coordinates underpin everything in modern geodesy. 100% agree, especially with orbital lidar, which is the preferred system to collect in.

While Vesta, Ceres, and Mars actually are good examples, I feel for this documentation, an Earth-based example will go further. While our community, planetary domain, commonly defaults to geocentric, we also often fit a best-fit-sphere for more irregular bodies specifically for cartographic (mapping) purposes. Thus geocentric and geographic are equal.

-Trent

On Tue, Jun 11, 2019 at 3:24 PM Emmanuel Devys notifications@github.com wrote:

Roger Lott (12/06) Geocentric coordinates underpin everything in modern geodesy. All other coordinates are derived from them. If GeoTIFF v2 ever comes to pass we will extend the list of (codes for) Model CRS types and geocentric will definitely be there. So it would be madness to deprecate it in v1.1. And I would say that to deprecate would be out of scope of the v1.1 revision. One of the reasons that examples are scarce may be that imagery is still in a 2D + 1D paradigm. I cannot see why retaining geocentric as a model CRS type must require an example: why? If it is only because no-one knows what they are then that is not an adequate reason.

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[adoyle]

Here are gdalinfo outputs on two of the Vesta files Steve had mentioned.

https://trek.nasa.gov/vesta/TrekWS/rest/cat/data/stream?label=Vesta_Dawn_HAMO_Shade_DLR_Global_48ppd_IAU https://trek.nasa.gov/vesta/TrekWS/rest/cat/data/stream?label=Vesta_Dawn_HAMO_Shade_DLR_Global_48ppd_IAU

% gdalinfo Vesta_Dawn_HAMO_Shade_DLR_Global_48ppd_IAU.tif Driver: GTiff/GeoTIFF Files: Vesta_Dawn_HAMO_Shade_DLR_Global_48ppd_IAU.tif Size is 17281, 8641 Coordinate System is: GEOGCS["GCS_VESTA_2013", DATUM["VESTA_2013", SPHEROID["VESTA_IAU_2013",255000,0]], PRIMEM["Reference_Meridian",0], UNIT["degree",0.0174532925199433]] Origin = (-180.010416666666657,90.010416666666671) Pixel Size = (0.020833333333333,-0.020833333333333) Metadata: AREA_OR_POINT=Area Image Structure Metadata: INTERLEAVE=BAND Corner Coordinates: Upper Left (-180.0104167, 90.0104167) (180d 0'37.50"W, 90d 0'37.50"N) Lower Left (-180.0104167, -90.0104167) (180d 0'37.50"W, 90d 0'37.50"S) Upper Right ( 180.0104167, 90.0104167) (180d 0'37.50"E, 90d 0'37.50"N) Lower Right ( 180.0104167, -90.0104167) (180d 0'37.50"E, 90d 0'37.50"S) Center ( 0.0000000, 0.0000000) ( 0d 0' 0.01"E, 0d 0' 0.00"N) Band 1 Block=17281x1 Type=Byte, ColorInterp=Gray NoData Value=0

https://trek.nasa.gov/vesta/TrekWS/rest/cat/data/stream?label=Vesta_Dawn_HAMO_TrueClr_DLR_global_74ppd_IAU https://trek.nasa.gov/vesta/TrekWS/rest/cat/data/stream?label=Vesta_Dawn_HAMO_TrueClr_DLR_global_74ppd_IAU

% gdalinfo Vesta_Dawn_HAMO_TrueClr_DLR_global_74ppd_IAU.tif Driver: GTiff/GeoTIFF Files: Vesta_Dawn_HAMO_TrueClr_DLR_global_74ppd_IAU.tif Size is 26640, 13320 Coordinate System is: GEOGCS["GCS_VESTA_2013", DATUM["VESTA_2013", SPHEROID["VESTA_IAU_2013",255000,0]], PRIMEM["Reference_Meridian",0], UNIT["degree",0.0174532925199433]] Origin = (-180.000000000000000,90.000000000000000) Pixel Size = (0.013513513513514,-0.013513513513514) Metadata: AREA_OR_POINT=Area Image Structure Metadata: COMPRESSION=LZW INTERLEAVE=PIXEL Corner Coordinates: Upper Left (-180.0000000, 90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"N) Lower Left (-180.0000000, -90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"S) Upper Right ( 180.0000000, 90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N) Lower Right ( 180.0000000, -90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"S) Center ( -0.0000000, 0.0000000) ( 0d 0' 0.00"W, 0d 0' 0.00"N) Band 1 Block=256x256 Type=Byte, ColorInterp=Red Band 2 Block=256x256 Type=Byte, ColorInterp=Green Band 3 Block=256x256 Type=Byte, ColorInterp=Blue

The data can be found at https://trek.nasa.gov/vesta/ https://trek.nasa.gov/vesta/ Click the search icon in the upper left, then click on a result to get to the download link.

On Jun 11, 2019, at 7:00 PM, Trent Hare notifications@github.com wrote:

>> Geocentric coordinates underpin everything in modern geodesy. 100% agree, especially with orbital lidar, which is the preferred system to collect in.

While Vesta, Ceres, and Mars actually are good examples, I feel for this documentation, an Earth-based example will go further. While our community, planetary domain, commonly defaults to geocentric, we also often fit a best-fit-sphere for more irregular bodies specifically for cartographic (mapping) purposes. Thus geocentric and geographic are equal.

-Trent

On Tue, Jun 11, 2019 at 3:24 PM Emmanuel Devys notifications@github.com wrote:

Roger Lott (12/06) Geocentric coordinates underpin everything in modern geodesy. All other coordinates are derived from them. If GeoTIFF v2 ever comes to pass we will extend the list of (codes for) Model CRS types and geocentric will definitely be there. So it would be madness to deprecate it in v1.1. And I would say that to deprecate would be out of scope of the v1.1 revision. One of the reasons that examples are scarce may be that imagery is still in a 2D + 1D paradigm. I cannot see why retaining geocentric as a model CRS type must require an example: why? If it is only because no-one knows what they are then that is not an adequate reason.

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[max-martinez]

[thareUSGS]

Yes ModelTypeGeographic is always the default. I'm not actually sure how to change that. But notice these are set as spheres so we can get away with it.

Mars is where we get into a lot of confusion and issues using ocentric/geographic on an ellipse. I would be happy to support an example for Mars (although still not sure how to set it myself)..

-Trent

On Wed, Jun 12, 2019 at 6:20 AM max-martinez notifications@github.com wrote:

[image: image] https://user-images.githubusercontent.com/46055544/59354539-54410680-8cf3-11e9-84c0-b8a9546b8895.png

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