Frequently Asked Questions

1.  Where can I get Tulalip GIS data?
Please ask the GIS Center for specific data you need about The Tulalip Tribes Reservation.
Visit our Contacts page for whom to call, or email us.
Visit our Services page for the services we provide and for request forms.
Visit our GIS Map Data page for information on ArcGIS map layers and how to get them.
Visit our GIS Resources page for forms and links on data, glossaries, tutorials and software.

2.  What coordinate system do we use at Tulalip Tribes?
In ArcGIS we use the Predefined Projected Coordinate System: NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet.
The following defines each component:

  • NAD 1983 – is the North American Datum created in 1983. It is based on the world Geodetic Reference System 1980 (GRS80) ellipsoid; an ellipsoid derived from satellites. A datum is defined by a spheroid, which approximates the shape of the Earth, and the spheroid's position relative to the center of the Earth.
  • State Plane – SPC is the coordinate system used in America. Each State is broken into zones with its own coordinates. SPCS was designed for a conformal mapping system for the entire country to maintain a maximum scale distortion of 1 part in 10,000. See State Plane Coordinate System image below.
  • Washington North - Washington has north and south zones. Tulalip Reservation is in the north zone. See Washington SPC Zones image below.
  • FIPS 4601 – is the Federal Information Processing Standards (FIPS) Codes for states derived by the U.S. Census Department of Commerce. The FIPS number 4601 is the SPC zone number for Washington North.
  • Feet – SPC uses the “U.S. Survey Foot”. It is almost exactly equal to a standard foot, but its definition is slightly different: 
    standard (or "international" ) foot:  .3048 meters
    U.S. survey foot: 1200/3937 meters

3.  World Coordinate Systems
Washington is in world UTM zones 10 and 11. UTM is the Universal Transverse Mercator world coordinate zone system in meters. Mercator created UTM system in 1569. UTM zones reach to the polar circles and count eastward to 60 from 180th longitude off the cost of Alaska around the globe and back.

The latitude of Tulalip is 48.068 degrees north of the equator and the longitude is -122.292 degrees west of zero degrees. Zero degrees longitude is at Greenwich, England where East meets West at the Greenwich Meridian Line. It is where Greenwich Mean Time (GMT) and time zones begin. 

For more information see Coordinate Systems Reference below or visit our Resources page.

4.  Why is a projected coordinate system important?
Distance measurements on the curvature of the earth are different than on a flat map. A straight line on the earth is a curved arc. A projected coordinate system adjusts for earth's curvature. Therefore distance measurements are more accurate by using a projected coordinate system. 

5.  Why use State Plane?
Government organizations and groups who work with them primarily use the State Plane Coordinate System. Most often, these are county or municipal databases. The advantage of using SPCS is that your data is in a common coordinate system with other databases covering the same area. –ESRI Trimble GeoXH 2005

6.  What is GPS?
GPS - Global Positioning System is a worldwide radio navigation system formed from a constellation of 24 satellites and their ground stations. GPS interacts with three or four satellites as reference points and a ground receiver to calculate positions on Earth which become data that can be used by GIS. Tulalip Tribes uses Trimble GPS technology to manage its utilities and other resources. Image: Trimble GeoXH 2005 (click image to enlarge)

State Plane Coordinate System
State Plane Coordinate System

 Image: James W. Merchant, Geog 412 class, Univ. of Nebraska (click image to enlarge)

The State Plane Coordinate System (SPCS) is a projected coordinate system that achieves greater accuracy by dividing states up into sub-zones based on county, and then uses a local projection in that sub-zone (typically Transverse Mercator for zones that are oriented more north-south, and Lambert Conformal Conic for those that run more east-west).

Washington State Plane Coordinate Zones

Washington State Plane Coordinate Zones

Washington North zone is in green and South zone is in pink. (click image to enlarge)
Image: Washington State Plane Coordinate Zones Map by the Tulalip Tribes GIS Center

Coordinate Systems Reference