Swiss Grid Issue - repost

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hover Global Mapper UserTrusted User
in Technical Support
In Switzerland, current "Swiss Grid" (Datum: SWISS GRID (CH1903)) projection is replaced by new "Swiss Grid (LV95)" (Datum: SWISS GRID (CH1903+).

I load a geo-referenced orthofoto into the workspace based on the new Swiss Grid (LV95) / CH1903+ projection. I pinpoint my GCP (ground reference point) with the cursor and put down the coordinates: 2623387.07 / 1167444.24 (+/- 0.02m). Then I change the display projection (Tools, Configure) to the old Swiss Grid ( CH1903) projection and do the same, the corrdinates now read 623387.03 / 167444.31. 

I then feed the original LV95 coordinates into NAVREF (https://www.swisstopo.admin.ch/de/karten-daten-online/calculation-services/navref.html), the swisstopo reference converter and convert them into the old projection (LV03) too. The result: 623387.01 / 167444.54.

Unfortnately, the two converted coordinates are not the same:
- 623387.03 / 167444.31 : converted by Global Mapper
- 623387.01 / 167444.54 : converted by swisstopo conversion reference app

While the X-coordinate is almost the same, the difference of the y-coordinate is signifficant, more than 0.2m.

How is that possible? Is there an issue with one of the two projections?
Am I missing something?
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Comments

  • bmg_bob
    bmg_bob Global Mapper Programmer
    Hello,

    Your message doesn't indicate what version of Global Mapper you are using.  If it is Global Mapper 17, please make sure that you have the latest version.  If your problem persists in the most recent release, please contact Blue Marble Geographics Support via e-mail (geohelp@bluemarblegeo.com), including a detailed description of your workflow (as in your post) and data that can be used to reproduce the problem.

    Cheers,
    Bob

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