This makes me uninstall Geocart 3!

[Piotr]

Additional meridians don't render when they coincide with one of the normal meridians! Please fix this!

[Atarimaster]

My guess is that Geocart, when it checks the Graticule dialog input values for errors, regards this as a mistake – »Why add a meridian that’s already there?«
Furtherly, I guess that your idea is to use a different color (via Line Styles dialog) for a certain meridian that’s within the defined meridian spacing.

If that is the case, a workaround would be to list the meridian in question to the "excluded meridian" list, and then add a meridian that’s only a little bit off; e.g. put 15°W to the excluded meridians, and 15°0'0.0001"W to the additional meridians.

[Piotr]

Yes - specifically I want to extend the coloring of 0 degree meridian to 180 degree meridian. The entire great circle is shown as straight line for example in transverse projections.

[Atarimaster]

Aaah! Describing your problem like this made me think of a better way:
Use a metric line database!
Refer to Appendix J of the Geocart manual to learn how to work with them. The content of the database file you need looks like this:

Code: Select all

<metric_lines>
	<layer alpha='0.8'>
        <great_circle center='0,90' />
	</layer>
</metric_lines>

After you’ve added the database file to the map, you can use the Line Styles dialog to set the color of the great circle.
Here’s an example of the result:

[Piotr]

What do you mean by "added the database file to the map"?

[Atarimaster]

What do you mean by "added the database file to the map"?

Opening the Map -> Databases… dialog, hitting one of the Add […] database buttons and select the database file.
You need to create that file first (maybe I wasn’t clear enough on this).

[daan]

Great explanations and suggestions, Tobias!

Best,
— daan

[Piotr]

VectorDatabaseReader: Polygon preface must contain two names separated by a tab, and then the count of points

[daan]

VectorDatabaseReader: Polygon preface must contain two names separated by a tab, and then the count of points

That’t true of a text database. However, if you’re doing what Tobias suggested, then you shouldn’t get this error because you wouldn’t be using a text database.

A metric lines database must have its extension be “.metric.txt”

— daan

[Piotr]

The extension is .txt and name ends on metric.txt so I don't see what's wrong.