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Mapping

Posted on 2002-07-08
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Last Modified: 2011-10-03
I want to write a GIS application where I have to find a location corresponding a given latitude and longitude.
I have placed the map in a picture box. I know the latitude and longitude of the top/left and bottom/right corner of the map.
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Question by:Gopakumar
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Expert Comment

by:ebosscher
ID: 7137647
And you know the width and the height of the picture box?  Umm.. why not do some quick math on the numbers

I don't know what the lattitude and longitude numbers are, but if you can give me an example I can show you the math.  

basically width / (lower right longitude - upper left longitude)

width = 800
ul long = 100
lr long = 105

800/(105-100) = 160  so, you have 1 additional point of longitude for every 160 horizontal pixles

the same math would work for lattitude.

does that help?
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Accepted Solution

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Ark earned 200 total points
ID: 7139421
Hi
First of all it depends on latitude range. On Mercator projection latitude scale isn't proportional. If range isn't large (up to 4 degrees), you may consider it is, so the easiest way is to set:

Picture1.ScaleMode = 0 'User
Picture1.ScaleLeft = LeftValue
Picture1.ScaleTop = TopValue
Picture1.ScaleWidth = RightValue - LeftValue
Picture1.ScaleHeight = BottomValue - TopValue

Now all your map is scaled according your coordinates and all mouse events (move, click, down/up) will return scaled values.
But if you need large range (more then 5 degrees) or very precissious coordinates, you have to use Mercator's projection formulaes.

Cheers
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by:DanRollins
ID: 7991189
Hi Gopakumar,
It appears that you have forgotten this question. I will ask Community Support to close it unless you finalize it within 7 days. I will ask a Community Support Moderator to:

    Accept Ark's comment(s) as an answer.

Gopakumar, if you think your question was not answered at all or if you need help, just post a new comment here; Community Support will help you.  DO NOT accept this comment as an answer.

EXPERTS: If you disagree with that recommendation, please post an explanatory comment.
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Expert Comment

by:SpideyMod
ID: 8053151
per recommendation

SpideyMod
Community Support Moderator @Experts Exchange
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