Magnetic Isolines (Production Mapping)
Summary
Creates isomagnetic lines in an extent for a date between 1/1/2005 and 12/31/2014 based on the World Magnetic Model. The tool uses a magnetic field parameter and line generation method to create a new polyline feature class.
Usage
Input Extent Feature Class or Raster can be points, lines, polygons, or a raster.
The Altitude value must be between 0 and 1,000,000.
If Output Feature Class already exists, the tool will append features to it.
The Magnetic Field Parameter lists the magnetic value types and output units that the tool can calculate.
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The Magnetic Field Parameter's Grid Variation (Decimal Degrees) option requires that a Lambert Conformal Conic projection be set in one of the following environments:
- The ArcMap data frame
- Geoprocessing Environment Settings > Cartography > Cartographic Coordinate System
- Geoprocessing Environment Settings > Output Coordinates > Output Coordinate System
- The coordinate system of Input Feature Class or Raster
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Raster Cell Size determines the number of cells in rasters used or created by the tool. The tool divides the shortest dimension (width or length) by Raster Cell Size to calculate the number of cells.
The tool will compute a default Raster Cell Size once you set Input Extent Feature Class or Raster and Magnetic Field Parameter. The tool computes a default cell size by dividing the shortest dimension of the input extent by 50.
In the Isoline Interval section, you must set the Base Value and Interval parameter or only the Isoline Values parameter. You cannot set all three. If you set Base Value but not Interval, the tool will display a validation error.
Syntax
| Parameter | Explanation | Data Type |
in_extent |
The feature class, feature layer, elevation raster, or elevation raster dataset for which you want to generate isolines. | Feature Layer; Raster Layer |
in_where_clause (Optional) |
A Structured Query Language (SQL) where clause that filters in_extent features based on attribute values. | SQL Expression |
in_altitude |
The elevation data required by the tool. The tool ignores this value if in_extent is an elevation raster. | Double |
in_altitude_unit |
The linear unit of measurement to use for altitude. Linear units include CENTIMETERS | DECIMAL DEGREES | DECIMETERS | FEET | INCHES | KILOMETERS | METERS | MILES | MILLIMETERS | NAUTICAL MILES | POINTS | UNKNOWN | YARDS. | String |
in_date |
The date for which you want magnetic field values to be calculated. The date must be between 1/1/2005 and 12/31/2014. Type the date in MM/DD/YYYY format. | Date |
out_features (Optional) |
The output polyline feature class. This feature class will contain the isomagnetic data created by the tool. The tool will create a feature layer from the feature class. The tool will overwrite existing data with the same name. | Feature Class |
in_output_subtype (Optional) | The subtype in the out_features that will store the isomagnetic data. You can set this parameter if out_features already exists. | String |
in_output_field (Optional) | The output field that will store the magnetic values. You can set this parameter if out_features already exists. | Field |
in_magnetic_field |
The magnetic field value computation type and output units.
| String |
in_cell_size |
The cell size for either the input data or a temporary raster created by the tool for non-raster input data. | Double |
in_base_value (Optional) |
The base value used to start generating lines. The tool computes values based on the generation method chosen in magnetic_field. The tool then creates a line from all points that match the base value. For example, if you choose Declination(Decimal Degrees) from magnetic_field and a base value of 0, the tool will first create isolines from all points with a declination value of 0. This parameter requires that you set the isoline_interval parameter. | Double |
in_isoline_interval (Optional) |
Specifies the increment value used to generate lines after the base_value line. For example, if you set Declination(Decimal Degrees) for magnetic_field, a base_value of 0 and an isoline_interval of 2, the tool creates a base isoline from all points with a declination value of 0, then isolines from points with declination values of 2. Use this parameter with base_value. | Double |
in_isoline_values [in_isoline_values,...] (Optional) | A list of magnetic values used by the tool to create isolines. The tool creates an isoline for each magnetic value in the list. Do not use this parameter with the base_value and isoline_interval parameters. | Double |
Code Sample
The following Python window example demonstrates how to execute the MagneticIsolines function using Production Mapping sample data. Run this script from either ArcMap or ArcCatalog. Make sure you enable the Production Mapping and Spatial Analyst extensions.
# paths to data
ElevP = "C:\\data\\SoCal_sample.gdb\\SoCal\\ElevP"
ElevP_Layer1 = "ElevP_Layer1"
magneticOut = "C:\\data\\work.gdb\\magneticOut"
# make a feature layer from the ElevP feature class
arcpy.MakeFeatureLayer_management(ElevP, ElevP_Layer1, "\"OBJECTID\" < 11")
# import the production mapping toolbox - you may have to alter this path
arcpy.ImportToolbox('C:/Program Files/ArcGIS/Desktop10.0/ArcToolbox/Toolboxes/Production Mapping Tools.tbx')
# Execute MagneticIsolines, writing the output to magneticOut
arcpy.MagneticIsolines_production(ElevP_Layer1, "", "100", "Feet", "3/10/2009", magneticOut, "", "", "Declination(Decimal Degrees)", "0.005", "0", "0.002", "")