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Common Questions About ArcGIS

 

  1. How to calculate acreage?
  2. How do I display the polygons in a theme according to a timber type (pine = green, water = blue, etc...)?
  3. How do I make the polygon theme transparent so I can see the underlying data?
  4. How do I make a map from my data?
  5. What should be included on my map? 
  6. Q&A from Senior Project Lecture (Feb 03, 2009)

1.  How to calculate acreage?

  • Your layer must have a defined coordinate system (see next entry)
  • From your layer's attribute table: 
    • Options > Add Field
      • Float should be the field type
    • Right-click (on the new field's header) > Calculate Geometry
      • change the Units: to Acres (NOT ARES), Hectares, etc. 
      • hit OK to calculate

 

2.  How do I display the polygons in a theme according to a timber type (pine = green, water = blue, etc...)?

  • Open your layer's attribute table
  • Add a new field (options > add field)
  • Attribute the polygons accordingly (type 1 gets value 1, type 2 gets value 2, etc)
  • In the Layer Property dialog (right-click on layer name > properties)
    • Select the Symbology tab
    • Specify Categories (left window)
      • change the Value's field to the one representing the attribute you want to display
      • 'Add All Values' or 'Add Value'
      • tweak the colors accordingly

 

3.  How do I make the polygon theme transparent so I can see the underlying data?

  • Open the Layer Property dialog (right-click on layer > properties)
  • Under the Display tab, adjust the number in the transparency box
    • larger number means the layer will be more transparent

 

4.  How do I make a map from my data?

 

5.  What should be included on my map?

  • north arrow
  • scale bar
  • legend
  • map frame
  • citations/credits (who made the map, the source data, etc)
  • map title

Q & A (Senior Project Lecture - Feb 3, 09)

How to change the collars of the NAIP imagery from black to clear?

  • Right-click on the layer's name > Properties
  • Click the Symbology tab
  • Check the box next to "Display Background Value..."
  • Hit OK

How to clip an image using a boundary polygon?

  • Open ArcToolbox
  • The EXTRACT BY MASK tool is under:  Spatial Analyst Tools > Extraction > Extract by Mask

How to combine features stored in many themes into one?

  • Open ArcToolbox
  • The MERGE tool is under:  Data management Tools > General > Merge
  • You can only merge like-type shapefile (you can not merge a polygon and a line shapefile)

How to save the symbology (color, shading, sizing, etc) of a shapefile?

  • Symbolize the shapefile how you want it
  • Right-click on the layer's name > Save As Layer File... (name it, specify your project folder, hit OK)
  • This creates a file (with a .lyr extension) that you can load just like a shapefile.  When you do, ArcMap will symbolize it accordingly. 
  • If you want to copy it to another computer, you must copy the layer file AND the shapefile
  • THE LAYER FILE DOES NOT STORE THE SHAPEFILE INFORMATION.  IT IS ONLY A FILE THAT CONTAINS A LINK THAT ArcMap CAN USE (BUT NO SHAPEFILE)

How to get the GPS data from the unit to ArcMap?

  •  This link ( www.warnellgis.com/node/54 ) will point you to instructions on how to use the GeoXM and ArcPad, Pathfinder Office, the GeoExplorer 3 units, and other useful GPS links.
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