MapWindow:Desktop:UpdateMeasurements

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Create or Update Length, Area or Perimeter Attributes

The Update Measurements tool is an additional plug-in which allows users to calculate line length or polygon area and perimeter, and add these to the attribute table. Users will need to download the plug-in and switch it on. This installs the Update Measurements Image:update-icon.jpg icon on the toolbar.

Calculate Line Length

To add a field in the attribute table which contains the length of the lines;

- Click on Update Measurements Image:update-icon.jpg icon

- The Update Measurements box appears

Image:update-line.jpg

- Select the layer to update from the list

- Select the correct shapefile units (if not already populated)

- Select the units for the calculations to be made in, ie Meters, Kilometers, Feet etc

- To use an existing field in the attributes, select ???Existing??? and the field name from the list

- To create a new field, select ???New???

o Length will be added by default to the name, or rename to preferred

o select the number of decimal places

- Click [Update Measurements] button

If further layers are to be updated, then repeat as above, or click [Close] button to close box.


Calculate Polygon Area & Perimeter

To add a field in the attribute table which contains the area and/or perimeter of the polygon;

- Click on Update Measurements Image:update-icon.jpg icon

- The Update Measurements box appears, with perimeter and area calculation options

Image:update-ply.jpg

- Select the layer to update from the list

- Select the correct shapefile units (if not already populated)

- Select the units for the calculations to be made in. Note ??? meters is the default for Perimeter units if Hectares is selected, or Feet is the default if Acres is selected.

- For each of either Area or Perimeter

- To use an existing field in the attributes, select ???Existing??? and the field name from the list

- To create a new field, select ???New???

o Length or Area will be added by default to the name, or rename to preferred

o select the number of decimal places

- If either field is not required, select ???None??? for these

- Click [Update Measurements] button

If further layers are to be updated, then repeat as above, or click [Close] button to close box.


Polygon Areas ??? GIS Tools option

If users only require Polygon Areas to be calculated, without the need for additional plug-in;

- Click on [GIS Tools] then click on [Vector]

- Click on [Calculate Polygon Areas]

- If it cannot detect the shapefile units a warning will show asking if you wish to use the units in the projection. Click OK

- The calculate area box appears

Image:image117.gif

- Select the layer.

- Set the shapefile units

- Set the units of the area the user want created

- If this is the first time, select the 'Use a new field' and give it a new name if required

- If there is already an area field, select 'Update an existing Field', and select the field from the list

- Click on [Calculate]

Your field will now have the area calculated.

The option to specify decimal places is not in this tool. To specify decimal places, use the Update Measurements Plug-in as above.

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This page has been accessed 2,209 times. This page was last modified on 29 January 2008, at 11:04.