# Map Projection

2 replies to this topic

### #1 Franz Posted 23 February 2011 - 10:34 AM

Franz

Newbie

• New Member
• 2 posts
• No Country Selected

Hello,

I don't know if this is the right forum to ask this question, but I'll give it a try...

I do some simulations for a wireless communication network with a tool that provides the received power level for each rasterpoint in an 25x25km area.
It does not give me the position of each value but the gps positions of the boundary of this area. So I got the latitude for the north and south border and longitude for west and east border.
Lets assume we have a 1000x1000 raster of level values in this 25x25km area. So what I want to do is to get to know the exact position of each raster-point.

The first thought I had was to get the 1000th part of the west-east-distance (lets just call it "step") and in case I want to know the position of the "middle", I just calculate westposition + 500*step.
But now I got a little bit confused with those different mapping projections. The simulation output says "UTM32"-projection. I know UTM is neither equal area nor equidistant, so I'm not sure if I just can approximate this small area of 25x25km as equidistant like I did above or not.
Is there a way to get the real position calculated from those information I got?

### #2 David Medeiros Posted 23 February 2011 - 11:22 AM

David Medeiros

Hall of Fame

• Moderator
• 1,314 posts
• Gender:Male
• Location:Redwood City CA
• Interests:Cartography, wood working, wooden boats, fishing, camping, overland travel, exploring.
• United States

Hello,

I don't know if this is the right forum to ask this question, but I'll give it a try...

I do some simulations for a wireless communication network with a tool that provides the received power level for each rasterpoint in an 25x25km area.
It does not give me the position of each value but the gps positions of the boundary of this area. So I got the latitude for the north and south border and longitude for west and east border.
Lets assume we have a 1000x1000 raster of level values in this 25x25km area. So what I want to do is to get to know the exact position of each raster-point.

The first thought I had was to get the 1000th part of the west-east-distance (lets just call it "step") and in case I want to know the position of the "middle", I just calculate westposition + 500*step.
But now I got a little bit confused with those different mapping projections. The simulation output says "UTM32"-projection. I know UTM is neither equal area nor equidistant, so I'm not sure if I just can approximate this small area of 25x25km as equidistant like I did above or not.
Is there a way to get the real position calculated from those information I got?

I'm confused, you have bounding boxes for each cell or you have raster dataset with a bounding box for the total raster area? Either way you can calculate the center point of each cell in ArcGIS fairly quickly, if you have access to the software.
GIS Reference and Instruction Specialist, Stanford Geospatial Center.

www.mapbliss.com
@mapbliss

### #3 Franz Posted 24 February 2011 - 04:06 AM

Franz

Newbie

• New Member
• 2 posts
• No Country Selected

I'm confused, you have bounding boxes for each cell or you have raster dataset with a bounding box for the total raster area? Either way you can calculate the center point of each cell in ArcGIS fairly quickly, if you have access to the software.

Right, I have raster dataset with a bounding box for the total raster and want to know the position of each raster point. I also would like to calculate the border position of smaller equal area boxes inside this box. Lets say I want to split this 25x25km area in 25x25 one square kilometer areas. And I need to know if there is some special calculation rule to do this!? Unfortunately I do not have ArcGIS...

Thanks

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

-->