1. CAD to GIS Data Integration Part 1 Datum, Projection, Coordination Systems Presented by Doug Howe, PLS April 24, 2015

2. Workshop Outline Why Surveyors use ground coordinate systems The 6 coordinate system parameters you need to know and understand Grid to Ground Coordinate System Conversions Scale Factors (Grid, Elevation, and Combined) Creating prj files for Ground Coordinate Systems ―Modified State Plane ―UTM ―Local Projections Tips and Tricks for assigning and modifying prj filesTips and Tricks for assigning and modifying prj files

3. Why do Surveyors use Ground Coordinate Systems? Grid Coordinate Systems are derived at mean Sea Level where the ellipsoid of the earth is smaller than at elevation X. In other words, distances on the ground at elevation X are longer than distances at sea level. Surveyors want to work in feet/cartisian coordinates, not Lats and Longs. Easier Calculations for area, slope and distance. Graphic Provided by:http://en.wikipedia.org/wiki/Mercator_projection

4. 6 Projected Coordinate System Parameters You Need to Know 1) Datum 2) Projection Type 3) Latitude and Longitude of Origin 4) False Northing and False Easting 5) Scale Factor 6) Units (International feet vs US Survey Feet) Graphic Provided by:http://en.wikipedia.org/wiki/Mercator_projection

5. Datum 3 Common Geographic 2D Datums in North America – Ellipsoids/Spheriod CLARKE 1866 (NAD27) a = 6,378,206.4 m a = 6,378,206.4 m 1/f = 294.97869821 1879 – 1986 GEODETIC REFERENCE SYSTEM 1980 - (GRS 80) (NAD83) a = 6,378,137 m 1/f = 298.257222101 1/f = 298.257222101 1986 – Present WORLD GEODETIC SYSTEM 1984 - (WGS 84) (GPS) a = 6,378,137 m a = 6,378,137 m 1/f = 298.257223563 1/f = 298.257223563 1987 - Present Graphic Provided by:http://en.wikipedia.org/wiki/Mercator_projection

6. Projection There are 2 commonly used projections by surveyors Mercator - Cylindrical Lambert Conformal Conic - Cone Colorado State Plane is a Lambert Project - Secant Graphic Provided by:http://en.wikipedia.org/wiki/Mercator_projection, accessed on April 5, 2015

7. Latitude and Longitude of Origin The position of any point on the earth or spheroid is represent by Latitude and Longitude. Origin of the coordinate system is at the intersection of the Longitude and Latitude of origin. Longitude of Origin aka Prime Meridian aka Central Meridian – extends North and South and represent the center of the grid plane east-west Latitude of Origin – extends East and West and represents the center of the grid plane north-south Standard Parallels – Lines of Latitude that intersect the ellipsoid, scale factor equals 1.00 (no distortion). Standard Line – Line of Longitude that intersect the ellipsoid, scale factor equals 1.00 (no distortion).

8. Latitude and Longitude of Origin Continued.. Graphic Provided by: Buckner, R.B., State Plane Coordinates in Modern Surveying Practice, August 1993.

9. Coordinates assigned to the origin of the coordinate system, the intersection of the Latitude and Longitude of Origin. Very Large Values to insure all coordinate values derived from the origin are positive. Surveyors usually confuse False Northing and Easting with the concept of coordinate truncation. Thank You Trimble! False Northing and Easting

10. Scale Factors Scale Factor is the ratio of length on the projection surface to the length on the ellipsoid. Used to compare distances on different surfaces, Grid and Ground for example. GRID (Ellipsoid) Scale Factor –Used to change geodetic (ellipsoid) distances to the grid plane. CORPSCON – Coordinate Conversion software provided by the US Army Corps of Engineers Can be used to calculate grid scale factor for any location with latitude and longitude Do not use CORPSCON to calculate a Combined Factor http://www.agc.army.mil/Missions/Corpscon.aspx ELEVATION Factor (a.k.a. Sea Level Reduction, Height Scale Factor or Ellipsoid Reduction Factor) – Used to change horizontal ground distances to geodetic (ellipsoid) distances Elevation Factor = r ÷ (r + h) r = Radius of the earth h= Elevation COMBINED Factor (a.k.a. Grid-Elevation Factor) – (GRID Scale Factor X ELEVATION Factor = COMBINED Factor) This factor changes horizontal ground distances to grid distances Based on Latitude and Elevations Where Surveyors apply the Combined factor causes problems for the GIS professional (Origin of Coordinate System, Center of Project, or at 0,0) https://www.youtube.com/watch?v=iwCAAsRvNW4

11. Ellipsoid Distance 12,514.16’ Grid Distance 12,513.851’ Ground Distance 12,517.521’ Distances Graphic Provided by: Hutchins, Chuck, “Gird to Ground”. Power Point Presentation, February 2015.

12. Units US Survey Feet Vs International Feet It is all about decimal places International Feet =.3048 Meters US Survey Foot = 1200/3937 Meters or.304800609601 One International foot equals 0.999998 U.S. Survey feet. OR One U.S. Survey foot equals 1.000002 International feet. It might not seem like much, but over a distance of miles this adds up. International Feet or US Survey Feet? What is the deal? International Feet or US Survey Feet? What is the deal?

13. Grid to Ground Coordinate Conversion, Origin of Scale Scale from center of project (Trimble Method) 1750586.523 x Ground Combined Scale Factor 3158678.258 x Ground Combined Scale Factor Does not work well with ESRI prj files Use Local Projection in this instance Spread Sheet Method or Scaled from 0,0 1000000.000 x Ground Combined Scale Factor 3000000.000 x Ground Combined Scale Factor Works well with ESRI prj files X, Latitude of Origin Y, Longitude of Origin 0,0 1750586.523 3158678.258

14. In order to inform down stream users of your data as to how you created you prj file, add the coordinate system parameters to the meta data file. Include a short description of your methods. Describe the intended uses of your data and the spatial accuracy one should expect when using the data. Meta Data Compilation

15. Resources http://support.esri.com/en/knowledgebase/techarticles /detail/32939 http://support.esri.com/en/knowledgebase/techarticles /detail/32939 “State Place Coordinates in Modern Surveying Practice”, by R.B. Buckner, PHD “Datums and Map Projections for Remote Sensing, GIS and Surveying”, 2 nd Edition, by Jonathan Iliffe and Roger Lott “Lining Up Data in ArcGIS, a guide to map projections” by Margaret M. Maher