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converting decimal degrees to miles, kilome...   Duane Griffith Apr 24, 2003
Re: converting decimal degrees to miles, ki...   Peter Krembs Apr 24, 2003
Re: converting decimal degrees to miles, ki...   Duane Griffith Apr 24, 2003
Re: converting decimal degrees to miles, ki...   Peter Krembs Apr 24, 2003
Re: converting decimal degrees to miles, ki...   Duane Griffith Apr 25, 2003
Re: converting decimal degrees to miles, ki...   Peter Krembs Apr 25, 2003
Re: converting decimal degrees to miles, ki...   raymond quiroz Oct 31, 2003
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Subject converting decimal degrees to miles, kilometers, 
Author Duane Griffith 
Date Apr 24, 2003 
Message I have been working with two layers of point data and trying to find the distance between all combinations of points on each layer. I received a VBA script from someone else and was able to modify it to make it find the distance but the value returned in the finished table is in decimal degrees, same units as the base map.

I have tried to rest the base map so distances are measured in mile, meters, etc by setting the base layer projection before loading the point data layers (each point identified by lat/long) and the map is displayed correctly, the map units are reported in meters and distances are measured in meters with the measure tool. However after running the VBA macro, the value returned is still in decimal degrees.

Is there a way to set the map unit so that it reports the right units (units I want) after running the macro?

Is there an easy way to convert decimal degrees to feet, meters, miles, kilometers (something I understand) outside of ArcMap?

Any help would be appreciated. Thanks in advance. 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author Peter Krembs 
Date Apr 24, 2003 
Message Hi Duane;

You'll want to convert your data to a projected coordinate system (i.e., non-geographic) if you want to take accurate measurements. As a general rule, Geographic projections are GIGO (garbage in, garbage out) and will not give you correct distances.

I suggest converting your point theme(s) into a State Plane or UTM projection. Then, you can get a more accurate measurement using any units you wish.

-Peter 
  Peter K. 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author Duane Griffith 
Date Apr 24, 2003 
Message I must be doing something wrong.

Steps I have taken:
1) load each point theme and save as a shape file
2) use ArcToolbox to save the new shape file(s) in
a state plane projection.
NAD27 Illionis west 1202
3) Modify the units of measure during step two
to display meters
4) load the newly projected shape files into ArcMap
5) right click on layers and change the coordinate system to the projection of the shape files including the display units of meters.


The points display correctly but use of the measurement tool gives me a distance of 36,600 meters from the western edge of Nebraska to eastern Ohio, approximately 22.7 miles.

Any ideas on what is going on here?

Thanks for any help.
 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author Peter Krembs 
Date Apr 24, 2003 
Message Duane;

If your original points are lat/long, you must first use the "Define projection Wizard" and define the shapefile as just a regular NAD83 if you haven't already. Any particular reason why your points are NAD27?

THEN you may convert them to whatever projection/coordinate system you'd like. 
  Peter K. 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author Duane Griffith 
Date Apr 25, 2003 
Message Still having trouble. Steps taken:

1) converted from Lat/long point file (file loaded as Access database then added points using Add XY coordinates)then converted to a shape file.
2) use Define Projection Wizard to define shapefile(s) as Projected, State Plane NAD83, East Illionis #1201 and accepted all defaults (linear units = meters). This was done in ArcToolbox
3) use the Project Wizard to project both shape files to state plane NAD83, East Illionis #1201 and accepted all defaults.
4) start with an new empty ArcMap screen
5) load newly projected shape files (everything looks fine)
6) right click layers for data frame and check coordinates system it is using = NAD83 state plane east Illionis #1201, linear units are meters, display indicates meters.
7) use the measure tool to measure the distance from the left most point (Western border of Nebraska) to the right most point (eastern Ohio)and I get a value of 22.6 meters.
8) right click layers and change the display unit to miles and measure again to get a value of .014xxxxx miles.

Any ideas????????????????

Thanks in advance.
 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author Peter Krembs 
Date Apr 25, 2003 
Message Duane;

In step two, you should be defining (use DEFINE Projection Wizard) your lat/long shapefile as NAD83, Geographic Projection. THEN reproject it into whatever you want using the Project Wizard.

 
  Peter K. 
   
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Subject Re: converting decimal degrees to miles, kilometers, 
Author raymond quiroz 
Date Oct 31, 2003 
Message Peter:

Thank you very much, I had the same problem and had worked on it for 2 days. Your solution was the the solution I had been looking for.