Mapping tabular data (Event Themes)


 


OCONEE FOREST PARK (Lake Herrick):  DATA DOWNLOAD LINK 


Here is the scenario:  You have been asked to compile preliminary data for the Oconee Forest Park for an upcoming project.  In the download above, you are provided three datasets:

  1. Lake_Herrick_Depths.csv: Lake depths captured with a Lowrance fish finder.  XY coordinates exported using Lat/Long, WGS1984, decimal degrees
  2. OFP_Features.txt:  Points of interest.  XY coordinates stored in Lat/Long, WGS1984, DMS
  3. OFP_TrailIntersections.txt:   Points within the forest where trails intersect.  XY coordinates stored in UTM/NAD 1983/Zone 17N/Meters

Your task is to prepare these data for further analysis.  Your map should look something like this when you are finished–>


NOTICE THE TABLE FORMAT


  • First row is the field names (no strange characters, no spaces, begin with A-Z, short, informative)
  • Remaining rows are data
  • Each column of data contain the same data types
    • either all numeric or all text
    • NAs can sometimes be troublesome

RECALL YOUR X’s & Y’s, NORTHINGS & EASTINGS, LATITUDES & LONGITUDES


Remember:

  • when you move from one line of latitude to the next, you are moving up the Y-axis
  • when you move from one line of longitude to the next, you are moving along the X-axis

  • there are 60 minutes in 1 degree and 3600 seconds in 1 degree; you must convert DMS to DD before you can plot the data in ArcMap
  • UTM “northing” values are the Y-variable, and “easting” values are the X-variable

ARCMAP WORKFLOW


  1. Create your working directory
  2. Start ArcMap
    • and set the Data View > Coordinate System to UTM/NAD1983/Zone17N
    • save your project to your working directory
    • create a new file geodatabase in your working directory
  3. Use Excel or R to convert DMS to DD (best to do it outside of ArcMap)
  4. Import your data files into the file geodatabase (TABLE TO TABLE tool in ArcMap)
    • check the data mapping to ensure fields are imported as the proper type
  5. Plot the XY coordinates (MAKE XY EVENT LAYER tool in ArcMap)
    • make certain that you specify the coordinate system that matches the XY’s you are importing
  6. Save the event themes out as feature classes in your file geodatabase.
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