Global Mapper Pro

France , Lambert-93-CC(42 to 50) , RGF-93

Geo
Geo Global Mapper UserTrusted User
edited April 2009 in Projection Questions
hello,

context

we use Global Mapper 9 to assemble cadastrals raster sheets.
the result is exported in one (occasionally more) file .tif and .tfw.

the projection used is Lambert 1 Nord (Northern France).

Since 3 March 2009, the "NTF France" should not be used for new productions. The new legal system is "Lambert 93" - "CC 42 to 50".
see "Lambert 93" project

Global Mapper 9 does not include build-in support for the use of this new system.

but, with Global Mapper 10, it is possible :

# Added support for users to add their own EPSG codes definitions or modify the existing ones by modifying the epsg_codes.txt file in the Global Mapper installation folder.

i made a try, updating the "epsg_codes.txt" file with :
3942,Lambert-93-CC42,RGF-93,meters,FIRST STANDARD PARALLEL=41.25,SECOND STANDARD PARALLEL=42.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=42,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=1200000
3943,Lambert-93-CC43,RGF-93,meters,FIRST STANDARD PARALLEL=42.25,SECOND STANDARD PARALLEL=43.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=43,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=2200000
3944,Lambert-93-CC44,RGF-93,meters,FIRST STANDARD PARALLEL=43.25,SECOND STANDARD PARALLEL=44.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=44,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=3200000
3945,Lambert-93-CC45,RGF-93,meters,FIRST STANDARD PARALLEL=44.25,SECOND STANDARD PARALLEL=45.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=45,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=4200000
3946,Lambert-93-CC46,RGF-93,meters,FIRST STANDARD PARALLEL=45.25,SECOND STANDARD PARALLEL=46.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=46,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=5200000
3947,Lambert-93-CC47,RGF-93,meters,FIRST STANDARD PARALLEL=46.25,SECOND STANDARD PARALLEL=47.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=47,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=6200000
3948,Lambert-93-CC48,RGF-93,meters,FIRST STANDARD PARALLEL=47.25,SECOND STANDARD PARALLEL=48.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=48,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=7200000
3949,Lambert-93-CC49,RGF-93,meters,FIRST STANDARD PARALLEL=48.25,SECOND STANDARD PARALLEL=49.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=49,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=8200000
3950,Lambert-93-CC50,RGF-93,meters,FIRST STANDARD PARALLEL=49.25,SECOND STANDARD PARALLEL=50.75,CENTRAL MERIDIAN=3,ORIGIN LATITUDE=50,FALSE EASTING (m)=1700000,FALSE NORTHING (m)=9200000
parameters can be also retrieved also from EPSG Geodetic Parameter Registry with Name : "RGF93 / CC"

the area in which I work is the Bas-Rhin in red on the map
bas-rhin.gif
it uses RGF93 / CC49

i made an ASCII Txt file containing the coordinates of the centroid of each town in this area

this file has been loaded in Global Mapper v10 with the projection "Lambert 1 Nord (Northern France)"
then the projection of the workspace was changed to "3949,Lambert-93-CC49" by using the "Init from EPSG" feature.

the same input was made with Circé which is an official IGN tool (see Résultats)
download is here : Logiciel Circé v3.2 pour la France Métropolitaine

and then the output coordinates where compared.
see the attachement "Transformation Grille_Global-Mapper vs CIRCE pour le 67.zip" (.xls file) for all details.

here is a graph showing the differences with Circé:

lambert93cc49globalmapp.png

it appears that for X, they are below the centimeter, and in Y, they are grouped around the value of 7.57 centimeters which is comparable to a constant.


question

we need to upgrade our Global Mapper v9 to have the Lambert-93-CC support.
but we have to obtain results with less than a centimeter error compared to Circé.

in the meantime we can use IGNMap to retroproject our assembly from NTF to Lambert-93-CC,
but we prefer to use only one software for this job because it takes a long time to create the .tif files twice.

an another trick could be to offset the coordinates of the .tfw file.

i hope you will be able to solve this problem,
and thank you for reading my poor english post.


Richard,
Cadastre surveyor in France.

Comments

  • global_mapper
    global_mapper Administrator
    edited April 2009
    Richard,

    I took a look at the NTF and RGF-93 transformations in Global Mapper and discovered that the NTF datums were setup to use the 'Clarke 1880' ellipsoid, rather than the very slightly different 'Clarke 1880 (IGN)' ellipsoid. This may account for the approximately constant offset that you are seeing. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with this corrected for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Geo
    Geo Global Mapper User Trusted User
    edited April 2009
    hello Mike,

    thank you very much, and congratulations for your reactivity!
    With this new version, the differences are negligible [dX -> 0.000 to 0.001], [dY -> -0.001 to 0.001]

    Do you think integrate the new projections french Lambert-93-CC in the Projection pull-down menu ?
  • global_mapper
    global_mapper Administrator
    edited April 2009
    It's good to hear the conversions are correct now. I will also go ahead and add the Lambert93 projections as built-ins to Global Mapper. I'll point you at a new build when that is ready.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapper
    global_mapper Administrator
    edited April 2009
    I have completed updating the built-in Lambert-93 projection to now be a zoned projection supporting the base Lambert-93 definition as well as the CC-42 through CC-50 zones. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the change for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Geo
    Geo Global Mapper User Trusted User
    edited April 2009
    Hello Mike,

    you have done a great job !

    I made the same tests with the same sample data for the version of 1 April 2009 of Global Mapper.

    In the sense NTF towards L93-CC49 and in the sense L93-CC49 towards NTF, the differences are the same as yesterday, ie [dX -> 0.000 to 0.001 m], [dY -> -0.001 to 0.001 m].

    thank you very much for the built-in Lambert93 projection zones in the pulldown menu ; it is much more pleasant to use this way.

    I congratulate you on the quality and the rapidity of your assistance as well as for the excellence your expertise.

    It is now time to contact our reseller in France and move to version 10.


    Richard,
    Cadastre surveyor, France.
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