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In preparing to create new or move existing feature classes into the new ArcGIS 9.2 geodatabase, several new spatial reference parameters must be addressed. The new 9.2 geodatabase modifies the 9.1 concepts of coordinate domain and precison, increases the range of values for these parameters using high precision coordinate storage, and introduces the concept of tolerance values in the geodatabase. Coordinate resolution (formerly precision) is the granularity with which coordinates can be stored. Tolerance is used for geoprocessing operations that look at relationships between features and is defined as the distance within which two coordinate locations are considered to be co-located (at the same position). In working with GIS data on the State Geographic Information Database (SGID) SDE database server maintained by AGRC, and for most project work, AGRC will be using the following standards for Spatial Reference parameters: Coordinate Tolerance -
XY, Z, & M Tolerance 0.1 Meters
Coordinate Resolution -
XY, Z, & M Resolution 0.01 Meters
Coordinate Domain -
X Min = -5120900 X Max = 90071987426509.9
Y Min = -9998100 Y Max = 90071982549309.9
Z Min = -100000 Z Max = 90071992447409.9
M Min = -100000 Z Max = 90071992447409.9
XY Coordinate System -
NAD_1983_UTM_Zone_12N
Z Coordinate System -
none These values will allow coordinates to be stored at 1 cm level precision and will direct geoprocessing operations to assume colocation of coordinates that are a distance of 10 centimeters or less from each other. Additionally, we do not recommend using the upgrade spatial referencing tool in ArcToolbox 9.2 as this doesn't provide the option of converting from our old 9.1 coordinate precision standard of 0.1 meters to our new 9.2 standard for coordinate resolution of 0.01 meters. Instead, create a new 9.2 geodatabase, transfer your schema definitions and set the new spatial reference parameters, and then load your data into the your new, empty 9.2 feature classes. For more information on the new Spatial Reference properties: http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=The_properties_of_a_spatial_reference
For more information on the new high precision coordinate storage in the 9.2 geodatabase:
http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Migrating_to_high_precision |
