Import
&
Conversion
among ArcMap layers, shape, raster and polygon
formats
Purpose:
Specific data formats (point, line, raster, polygon) are
required for various ArcMap
toolbox
functions.
Identifying the formats required for a desired function is the first
step
in using some of the many toolbox or modeling features in ArcMap. A
good place to start is to take 5 minutes for an overview
of geodatabase design.
Software/ Platform: ArcMap/
Windows only.
I.
Importing XYZ data into ArcMap Point Data Layer:
- ArcMap
can only import Comma-Separated Values, or CSV files - Tab delimited
files will not work. Data can be saved as a CSV file in programs such
as Microsoft
Excel (be sure to use labels for multi-column tables).
- CSV files for import cannot contain any extended ASCII characters
(only numbers and letters). To remove extended characters,
use a Unix/ Linux terminal window to execute the following tr filter to
remove all
non-printable ASCII characters:
tr
-cd '\11\12\40-\176' < $INPUT_FILE > $OUTPUT_FILE
- Add the CSV file to ArcMap using the Add Data button, at which
point it will be added as an ArcMap Layer. You must be under the Source
tab to view these files.
- Right click on the name of the new ArcMap layer and go to Display
XY Data. Set the X Field to longitude, the Y Field to latitude, and the
Geographic Coordinate System to WGS 1984.prj. Click OK and the data
will be displayed on the map as a new layer entitled Events.
- Point data can be controlled by right-click/ properties to
adjust symbology, data selection etc.
- Point data is a good format
for plots of station data for cruise tracks or to show data at
stations. Data can also be used
with other layers such as topography and coastlines. Additional
functionality requires that the file be
converted to a shape, raster or polygon format.
II. Point Layers
to
Shape files:
- Right-click/ Data/ Export data to save an ArcMap layer as a shape
file (.shp)
& 6 other associated files. (Make sure an appropriate coordinate
system has been applied before exporting).
- Shape files have all of the
features of a layer with the
important additional ability to do computations in the table
attributes.
III.
Shape
file or Point File to Raster:
- ArcToolbox/ Conversion Tools/ To Raster/ Point to Raster. This is
the simpliest method to generate a raster. THE RASTER
SHOULD BE COMPARED TO THE ORIGINAL DATA TO ENSURE THAT THE FEATURES
HAVE BEEN FAITHFULLY REPRODUCED. The cell size for the raster
interpolation can be adjusted to optimize interpolation.
- ALTERNATIVE METHOD TO GENERATE RASTER: Arc Toolbox/ 3D Analyst
Tools/ Raster Interpolation.
This contains a Kriging method. Kriging is the most accurate
translation method and may be required for sparse data sets that do not
interpolate well using the standard Point to Raster function.
- This rasterization process creates a folder with 6 files (7 for
Kriging) and a .xml file external to the folder.
- Rasters are one
of the the most useful formats for the analysis and modeling of
oceanographic data. They can be used for classification, grid math,
contouring (Spatial Analyst Toolbar), resampled (ArcToolbox/ Data
Management Tools/ Rater Processing/ Resample), various types of block
calculations (such as averaging to reduce resolution - ArcToolbox/
Spatial
Analyst Tools/ Generalization/ Aggregate).
IV.
Raster to Polygon:
- ArcToolbox/Conversion Tools/ From Raster/ Raster to Polygon - Not
yet verified - does not work with standard rasters from III - Need to
create integer raster first?
- Points to polygons; Verticies to Polygons
- Can draw new polygons from editor as new feature layer (line),
create new polyline - drag to map?
- Polygons make statistical
analysis faster - e.g. area, perimeter,
etc.