RE: [OpenMap Users] rendering problem still remains

From: Piotr Kamiński <>
Date: Tue, 5 Oct 2004 19:18:33 +0200

Don, I remeber that you wrote some time ago about changing float to
double in OpenMap.
Have you made any progress in that area? The problems Ruben has
described are just the same as
I have using small scales (1:100, 1:50). I think that increasing
precision of calculations is
really needed. I could participate in that work. I wonder if refactoring
(like RefactgorIt that we use in our company) could help in those big
Best regards,
Piotr Kaminski
-----Original Message-----
From: []
On Behalf Of Hudson Brian R Contr AFRL/IFSF
Sent: Tuesday, October 05, 2004 4:44 PM
To: Rubén Ruiz; Openmap Mailling-list
Subject: RE: [OpenMap Users] rendering problem still remains
Don gives some suggestions here on how to modify OpenMap to use doubles.
Many people seem interested in this, but I haven't heard of anyone doing
it successfully. Don indicates that is a large job.
I'm not sure that rendering in XY will help. When you are at that scale
OpenMap attempts to determine the XY location of things based on its
lat/lon. At that scale the lat/lon per pixel is so small that rounding
errors (and precision) can really mess up the drawing (as you can see by
using the drawing tool). You could attempt to use XY rendering but in
order to get the XY points won't you have to use the projection classes
to turn your lat lon points into XY coords? Doing this will cause you to
suffer the rounding/precision problems that OpenMaps lat lon render type
is having at the at scale.
You could possibly write your own lat/lon to xy function that would take
the scale and top left/bottom right lat lon points, then using doubles
calculate the delta per pixel, then using that information to calculate
the XY coords of your rendering in order to get a bit more precision.
Brian Hudson
-----Original Message-----
From: []
On Behalf Of Rubén Ruiz
Sent: Tuesday, October 05, 2004 9:22 AM
To: Openmap Mailling-list
Subject: [OpenMap Users] rendering problem still remains
Hi all,
Fitst of all i would like to thank to Brian Hudson for his
ideas...thanks brian.
When I use XY / XY-Offset Rendering type I can draw perfectly,
problem is not just when I'm drawing, I've a set of maps coming from
autocad, I've managed to translate them into shapefiles in Lat/Lon. The
problem comes with many lines/polygons using a high scale (1:62)
projection. The normal polygons are more or less "visible", but all my
circles are not. I don't know if I can change the rendering type for all
my lines/polys when I load them or anything similar. Also when I draw a
nice circle with XYOffset and I save it in a SHP, it really stores a
rectangle, and if I load that shp again I can see a perfect
rectangle...I cannot store nothing rendered with any XY render type.
At this point I've been thinking in varius exits to this problem:
- if its possible to render XY all my graphics I think it'll be
solved, but I've tried with no success...
- if it would solve this problem...could I change all float
members to double or is there any restriction that makes it impossible?
Do you know where can I begin to change and what portion of openmap do
I've to change? I think the main problem resides in the projection
classes but I need some "light" from you, I've not been working with
openmap too much, and every day I find new fancy things.
I hope someone can help me...
Thanks in advance,

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Received on Tue Oct 05 2004 - 13:55:37 EDT

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