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VVouter

Belgium
18 Posts

Posted - 26/01/2015 :  22:34:46  Show Profile  Reply with Quote
Hello,

The CRS of my digital map is ETRS89 / Belgian Lambert 2008 (EPSG::3812). The map does not show a grid.

I will use a paper map of the same area as a reference. The paper map has an UTM grid based on the ED50 datum (EPSG::23031)

I will try to align the calibration points with the UTM grid on my paper map. Should I use the "Grid setup" button to configure the UTM/ED50 CRS? Can I use the "Alt" tab to directly provide the UTM coordinates found on my paper map?

Is there a difference between the "Grid setup" button in the calibration wizard and the menu item Preferences > Grid > Set altern grid ?

Regards,

Wouter

okmap

Italy
2374 Posts

Posted - 27/01/2015 :  09:51:03  Show Profile  Visit okmap's Homepage  Reply with Quote
Grid setup button configures the grid drawn on the map; you can select a different projection / datum from that used for map calibration (Setup map button).
The Alt tab is used to input metric coordinated in the projection / datum of the map (Setup map button).
The Proferences - Grid - set Altern grid page is intented for that functions that doesn't involve a map such as coordinate conversions and other function in Utilities section.
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VVouter

Belgium
18 Posts

Posted - 28/01/2015 :  11:31:03  Show Profile  Reply with Quote
Hello,

I played a bit with the grid settings but got a bit confused.

I found this strange behaviour:

When I use "File>Modify>Grid Parameters>Copy from map" the status bar shows the cartesian coordinates according to the datum & projection of my map as expected. So far everything ok.

However, when I use "File>Modify>Grid Parameters>Clear alternative grid" 2 strange things happen:

1) The alternative grid interval is NOT cleared. The Map info still shows the alternative grid interval.

2) The status bar still shows cartesian coordinates and the numbers are now different than before. What do they refer to?

Regards,

Wouter
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VVouter

Belgium
18 Posts

Posted - 28/01/2015 :  13:25:28  Show Profile  Reply with Quote
But what is then the difference with "Copy from preferences" ?

Wouter
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okmap

Italy
2374 Posts

Posted - 28/01/2015 :  14:02:00  Show Profile  Visit okmap's Homepage  Reply with Quote
You have reason. I've deleted my previous answer because wrong.
Clear button doens't clear interval but set grid projection to nothing so no grid will be drawn on map.
Remember that OkMat manages the map datum/projection and the grid datum/projection that can be different.
The first one is used to calibrate map while the second one to draw grid on the map.
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VVouter

Belgium
18 Posts

Posted - 28/01/2015 :  15:07:52  Show Profile  Reply with Quote
It are the metric coordinates in the status bar that confused me.

When no alternative grid is defined (e.g. after alt grid clear), the metric coordinates in the status bar are UTM based on the MAP DATUM. Can you confirm this?

However, when an alternative grid is defined, the metric coordinates in the status bar are based on the alternative GRID DATUM/PROJECTION

It would be cleaner if the status bar would have designated fields for the different coordinates like:

|Lat-Lon map datum|metric map datum|Lat-Lon alt datum|metric alt datum|

If no alternative datum is specified, those fileds could stay empty.

It would also be useful to show all 4 grids on the map. E.g. Belgian topomaps use Belgian Lambert 72 for projection, but the Lat-Lon and UTM grids are based on ED50.


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okmap

Italy
2374 Posts

Posted - 28/01/2015 :  15:58:20  Show Profile  Visit okmap's Homepage  Reply with Quote
In the status bar you have 2 coordinates system.
The first can be set in preferences general and can be:
- Decimal degrees (map datum)
- Degrees, Decimal minutes (map datum)
- Degrees, Minutes, decimal seconds (map datum)
- Radiants (map datum)
- UTM (map datum)
- Alternative grid (grid datum/projection) (***)

The second is always
- Alternative grid (grid datum/projection)

When no alternative grid is defined OkMap use UTM coordinates system.

I could change the field (***) with map metric coordinates system.
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VVouter

Belgium
18 Posts

Posted - 28/01/2015 :  21:32:03  Show Profile  Reply with Quote
Hello,

I have put my comments inline.


The second is always
- Alternative grid (grid datum/projection)


Why not give the full selection for the second CRS too?

First coordinate field:
- Decimal degrees (map datum)
- Degrees, Decimal minutes (map datum)
- Degrees, Minutes, decimal seconds (map datum)
- Radiants (map datum)
- UTM (map datum)
- Metric grid (map datum/projection)

and second coordinate field:

- Decimal degrees (alt datum)
- Degrees, Decimal minutes (alt datum)
- Degrees, Minutes, decimal seconds (alt datum)
- Radiants (alt datum)
- UTM (alt datum)
- Metric grid (alt datum/ alt projection)

I could change the field (***) with map metric coordinates system.

Yes, I think that is a good idea since it is redundant

Ideally, the grid settings would be consistent with the coordinate settings on the status bar. So if the the first coordinate field is configured as lat-lon, draw a lat-lon grid. If the first coordinate field is configured as metric, draw a metric grid. And the same for the second coordinate field and second grid.

Regards,

Wouter
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okmap

Italy
2374 Posts

Posted - 29/01/2015 :  10:50:41  Show Profile  Visit okmap's Homepage  Reply with Quote
Yes your is a good idea.
Storically alt grid has been introduced after and the status bar was not rearranged.
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VVouter

Belgium
18 Posts

Posted - 29/01/2015 :  12:30:48  Show Profile  Reply with Quote

Also consider the following things:

File > Modify > Grid map parameters > Set alternative grid

and

Utilities > Preferences > Grids > Set alter. grid

have very similar name but very different settings. This is confusing.

Also for "Utilities > Preferences > Grids > Set alter. grid" it would be handy if the configuration is visible next to the button. Or maybe better, in the status bar?

For "Maps > List maps by position", what is the datum for the coordinates? Maybe always specify the used datum/projection in a coordinate box. E.g. also for "find > Coordinates". Now it is only available for the Alt coordinates tab.

Regards,

Wouter



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okmap

Italy
2374 Posts

Posted - 30/01/2015 :  09:10:30  Show Profile  Visit okmap's Homepage  Reply with Quote
In some cases (custom definition) datum/projection cannot be synthetized with a simple description and represent it needs a long description.
Utilities > Preferences > Grids > Set alter. grid is used in all that function without map (i.e. Utilities - Coordinate conversion, etc..).
However your message is clear, I need to specify better the different coordinates systems where them appears.
Thanks for reporting
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