I have a point feature shape file with some concentration values assigned to them. I want to assign the concentration to a 1 sq.km area with the point feature as its center. Can anyone give me some pointers in this direction?
Have you done the Step 4: Clip? I wonder if you can set the XY tolerance in Clip so that the two closely located vertices snap together, if the default xy tolerance is not enough.
Otherwise: - Run Integrate tool (Data Management toolbox - Feature Class toolset) with the XY tolerance large enough to get the two closely located vertices snap together. The result shapes may not be perfect squares. How critical is the shape to your analysis?
Try this: 1. Use 0.5 KM distance to produce buffers. 2. If you have ArcInfo license, use Feature Envelope To Polygon, using the buffers as input. The envelopes should be the squares you need. If you are using ArcGIS 10, you can also use Minimum Bounding Geometry tool with the geometry type, RECTANGLE_BY_AREA, to get the bounding square of the buffers. Both tools are in Data Management toolbox - Features toolset.
The method you have suggested has solved the issue. However, I have another issue.
The point features in my dataset are tilted. However, when i create the square buffers around these points, the squares are not tilted accordingly. Thus, this leads to inconsistent square buffers. Can you suggest me something in this regard. I am attaching the image files showing the issue.'
The first image shows the tilted point features and the second image shows the created square buffers that are not tilted.
You need to do some work to figure out the precise extents (corner coordinates) based on the corner points plus some offsets. The resulting fishnet will be tilted with the points at centers of the cells.
Ok, try the followign (still assuming points are equally spaced in both row and column directions):
1. Use 0.5 KM distance to produce buffers. 2. If you have ArcGIS 10, run Minimum Bounding Geometry tool (Data Management toolbox - Features toolset) on the buffers, specify RECTANGLE_BY_AREA for geoemtry type and ALL for Group Option. You will get one rectangle around all the buffers. 3. Zoom out so that you see a lot of while area around your points. Run Create Thiessen Polygons tool (Analysis toolbox - Proximity toolset; requiring ArcInfo license) on the points; make sure to set Environment ... - Processing Extents to be "Same as Display". You should get square polygons around points, except at the edges where the polygons fill up the display. 4. Use Clip tool (Analysis toolbox - Extract toolset) to clip the Thiessen polygons by the rectangle from Step 2 above.
Is the result what you need?
If you want to automate the "Zoom out" part of Step 3, you can just set a large extent values, so that the Thiessen polygons go out of the rectangle.