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how to create a shapefile from lat/long dat...   Jen B Jan 23, 2003
Re: how to create a shapefile from lat/long...   Stephen Lead Jan 23, 2003
Re: how to create a shapefile from lat/long...   Jen B Jan 23, 2003
Re: how to create a shapefile from lat/long...   Ianko Tchoukanski Jan 23, 2003
Re: how to create a shapefile from lat/long...   Stephen Lead Jan 23, 2003
Re: how to create a shapefile from lat/long...   kolli ravikanth Oct 23, 2005
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Subject how to create a shapefile from lat/long data? 
Author Jen B 
Date Jan 23, 2003 
Message I am a relatively new ArcView user (I have version 8.1) and am having difficulty converting data from a Microsoft Access file to a shapefile. My data consists of latitude/longitude coordinates of stations sampled in a body of water, and several descriptors about the location, one of which is a value of a water parameter (salinity). I was able to open the data as a personal geodatabase table in ArcCatalog and create a feature class using the XY table to create a point shapefile, which I could then overlay on a pre-existing map of the region. However, I would like to use the water parameter data to create a polygon or line shapefile to better represent how different regions of the water body vary by salinity. In other words, I'd like to join the points that have similar values. I have been unable to figure out how to even go about creating a polygon shapefile. Is it even possible to do with the data I have (I attached part of the original table)? Could anyone point me in the right direction? Thanks!! 
   
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Subject Re: how to create a shapefile from lat/long data? 
Author Stephen Lead 
Date Jan 23, 2003 
Message Hi Laurie,

This process will take a couple of steps.

The first step is to convert your tabular data to geographic data - ie, plotting the XY coordinates on the map.

Once you've brought the table into ArcMap, choose -> Tools -> Add XY Data. This will create an Event Layer, where ArcMap creates a point layer based on the XY coordinates.

You can convert this into a point shapefile (a GIS dataset stored on disk) by right-clicking and choosing -> Data -> Export Data.

Now that you have points representing the values in the table, there are a couple of ways to create a line or polygon dataset from the points.

To do this manually, you could create an empty line or polygon dataset, and digitize new lines/polygons over the points.

In ArcCatalog, choose -> File -> New -> Shapefile. In the Feature Type dropdown, specify whether you want to create a polyline or polygon dataset.

Add this empty dataset to ArcMap, and start editing. Open the -> Editor -> Snapping dialog and set the snapping environment to the vertices (points) of your points layer. Now when you digitize the lines or polygons, their vertices will snap to the existing points layer.

You may need to check the ArcGIS Help file for more detailed information on some of these steps, eg how to start editing, snapping, etc.

If you're feeling more adventurous, there is an automated method for converting points into polygons found in the ArcObjects Developers Kit under -> Samples -> Geometry -> Convert selected points to polygon. This may require a little more experience with ArcGIS, and possibly some VB/ArcObjects experience.

Good luck,
Steve 
   
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Subject Re: how to create a shapefile from lat/long data? 
Author Jen B 
Date Jan 23, 2003 
Message thanks for the info!! I'll give it a try

Laurie 
   
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Subject Re: how to create a shapefile from lat/long data? 
Author Ianko Tchoukanski 
Date Jan 23, 2003 
Message I think that a better way to achieve this is to create a surface using your water parameter as a Z value.
See this thread:
http://forums.esri.com/Thread.asp?c=93&f=982&t=83144&mc=1 
  http://www.ian-ko.com 
   
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Subject Re: how to create a shapefile from lat/long data? 
Author Stephen Lead 
Date Jan 23, 2003 
Message Good point - if the points represent salinity, the values will probably vary across your study area, and a raster will capture this more effectively for some types of analyses.

Once you have the salinity modelled in raster format you can reclassify it into distinct classes, and convert these into polygons.

Good luck,
Steve 
   
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Subject Re: how to create a shapefile from lat/long data? 
Author kolli ravikanth 
Date Oct 23, 2005 
Message i am presently working on a project for drawing shape files
could any one of u tell me how to access the complete coordinate set from the shape files for drawing
i am able to draw only a few of the coordinates and unable to access the points after encountering an epsilon floating value .
plz could anyone of u help ????? urgent..