Opened 6 years ago

Closed 6 years ago

#4115 closed defect (fixed)

Conversion of "Popular Visualisation CRS" projection in MapInfo tab file is faulty

Reported by: stevemargetts Owned by: warmerdam
Priority: normal Milestone: 1.9.0
Component: OGR_SRS Version: unspecified
Severity: normal Keywords: mitab Popular Visualisation CRS, MapInfo, Virtual Earth
Cc: dmorissette

Description

MapInfo? 10.5 allows the user to draw polygons on top of background images provided by Virtual Earth. If you do this, the resulting polygons have the "Popular Visualisation CRS" projection (EPSG: 3857).

When read by OGR, this projection is not converted correctly, resulting in a significant shift in the polygons. It appears that the spheroid definition is not set correctly, as it ends up being set to SPHEROID["unknown",6378137,298.257223563], instead of SPHEROID["Popular Visualisation Sphere",6378137,0]

The attached file should display this issue

Attachments (2)

Problem regions.zip (3.0 KB) - added by stevemargetts 6 years ago.
MapInfo? tab file showing the problem
problem regions MIF.zip (2.9 KB) - added by stevemargetts 6 years ago.
Problem regions in MIF format

Download all attachments as: .zip

Change History (5)

Changed 6 years ago by stevemargetts

Attachment: Problem regions.zip added

MapInfo? tab file showing the problem

comment:1 Changed 6 years ago by warmerdam

Cc: dmorissette added
Keywords: mitab added
Status: newassigned

Steve,

It seems this file has spheroid 54 while the highest we have a definition for is 51, and it has datum 157 while the highest we have is 152. Do you happen to know of a datum and/or ellipse definition table we could use to extend the mapinfo driver code?

If it is convenient I would also be pleased to have the same file translated to mif format with mapinfo.

Changed 6 years ago by stevemargetts

Attachment: problem regions MIF.zip added

Problem regions in MIF format

comment:2 Changed 6 years ago by stevemargetts

Thanks for the prompt response. I've uploaded a MIF export of the same data; the projection string is "CoordSys? Earth Projection 10, 157, "m", 0 Bounds (-40075016.6856, -20037508.343) (40075016.6856, 20037508.343)"

I'm afraid don't know the datum definition, but my guess would be that it's a mercator projection based on a sphere, as used by Virtual Earth (i.e., a radius of 6378137m with no flattening).

If it helps, the corresponding proj4 projection string seems to be "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs"

comment:3 Changed 6 years ago by warmerdam

Milestone: 1.9.0
Resolution: fixed
Status: assignedclosed

I have somewhat blindly implemented support for reading, but not writing google mercator based on these examples (r22524). Also upstreamed into mitab cvs.

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