ArcView 3.x – Projections and Datums

This document addresses some common questions related to working with shapefile projections in ArcView 3.x. As it were, there are only a handful of common projections used with GIS data in the Upper Susquehanna Watershed and only two datums. This document will focus on using the standard ArcView 3.x tools for dealing with projections and datum shifts.

It is extremely important for ArcView 3.x users to understand that ArcView's projection engine (prjctr.avx) does not inherently support datum transformation. The following is from the online help under "datums > working with datums":

"When a projection associated with a certain spheroid is used, ArcView assumes that the decimal degrees data being projected was collected in a datum based on that spheroid."

Thus, for example, if your data in Decimal Degrees (DD) were collected in NAD27 and you're attempting to project your view to a projection using NAD83, you will not get correct coordinates. Similarly, if you were to attempt to use ArcView's Projector! extension to convert between two projections based on different datums, you will not get correct results.

However, the Projector! extension will handle common re-projection of data within the same datum. The following tutorial document shows the standard procedures for re-projecting data common to the region using the Projector! extension.

ArcView 3.2 and 3.3 come with a standalone projection utility that supports most common datum conversions, including NADCON. It has a wizard-based interface but can also be invoked from the command prompt. The only datum shift used in this region is the NADCON conversion from and between NAD27 and NAD83. The second part of the tutorial shows how to use the ArcView Projection Utility to re-project data when datum shifts are involved.

The last part of the tutorial covers some of the common projections associated with Pennsylvania data and how to use both extensions to handle projection issues.

 

Standard Projections of GIS Data in the Upper Susquehanna Watershed

UTM NAD 83 Zone 18 Meters
UTM NAD 27 Zone 18 Meters
UTM NAD 83 Zone 17 Meters
UTM NAD 27 Zone 17 Meters
State Plane NAD 83 New York Central Feet
State Plane NAD 27 New York Central Feet
Geographic Decimal Degrees NAD 83 Meters
Geographic Decimal Degrees NAD 27 Meters
 

 

Re-projecting Shapefiles in the Same Datum Using the Projector! Extension

 

Re-project UTM NAD 83 Zone 18 Meters to State Plane NAD 83 New York Central Feet

Open windows explorer, navigate to the following folder,

C:\\ ESRI\AV_GIS30\ARCVIEW\Samples\ext and find the file prjctr.avx

Copy and paste this file into the following folder,

C:\\ ESRI\AV_GIS30\ARCVIEW\EXT32

 

Step 1. Click File > Extensions.

Step 2. Check on the Projector! Extension.

In the View window you will see the Projector! button added on the far right of the button bar.

Step 3. Highlight the theme to make it active. Click View > Properties.

Step 4. Set the Map Units to Meters. The distance units do not matter. Click OK.

Step 5. Click the Projector! button. You will see this dialog.

Step 6. Chose the input projection – Category: UTM - 1983, Type: Zone 18

Step 7. Choose the output units – For State Plane it would be Feet.

Step 8. Set output projection – Category: State Plane 1983, Type: New York , Central Click OK.

Step 9. Click No to Recalculate Area request.

Step 10. Click Yes to Add projected shapefiles to view.

Step 11. Choose the view you want the themes in.

Step 12. Save the new reprojected theme.

This will save the reprojected theme and load it into the View window.

 

Re-project Decimal Degrees NAD 83 to UTM NAD 83 Zone 18 Meters

Step 1. Click File > Extensions.

Step 2. Check on the Projector! Extension.

In the View window you will see the Projector! button on the far right of the button bar.

Step 3. Highlight your theme to make it active. Click View > Properties. Set the Map Units to decimal degrees. The distance units do not matter. Click OK.

Step 4. Click the Projector! button. Set the output units to meters and click OK.

Step 5. Choose the output projection – UTM NAD 83 zone 18, Click OK.

Step 6. Click No to Recalculate Area request.

Step 7. Click Yes to Add projected shapefiles to view.

Step 8. Choose the view you want the themes in.

Step 9. Save the new reprojected theme on your hard drive.

I usually name the new file xxxxxxx_83 so I know the projection

 

Re-project State Plane NAD 83 New York Central Feet to UTM NAD 83 Zone 18 Meters

Step 1. Click File > Extensions.

Step 2. Check on the Projector! Extension.

In the View window you will see the Projector! button added on the far right of the button bar.

Step 3. Highlight the your theme to make it active. Click View > Properties. Set the Map Units to Feet. The distance units do not matter. Click OK.

Step 4. Click the Projector! Button

Step 5. Chose the input projection – Category - State Plane, Type - New York Central

Step 6. Choose the output units – For UTM it would be meters.

Step 7. Set output projection. UTM NAD 83 zone 18 Click OK.

Step 8. Click No to Recalculate Area request.

Step 9. Click Yes to Add projected shapefiles to view.

Step 10. Choose the view you want the themes in.

Step 11. Save the new reprojected theme.

 

Re-projecting Shapefiles in Different Datums Using the Projection Utility Wizard

Re-project UTM NAD 83 Zone 18 Meters to State Plane NAD 27 New York Central Feet

Step 1. Click File > Extensions.

Step 2. Check on the Projection Utility Wizard

Step 3. Click File > ArcView Projection Utility…

The ArcView Projection Utility Wizard will initialize and open. Sometimes this can take a moment to load.

Step 4. Click the Browse… button and load the shapefile(s) you want to re-project. Click Next>

Step 5. On the Name tab click on Projected for the Coordinate System Type. In the Name section find the current projection of the shapefile from the dropdown list. Set the Units to the appropriate system. If your shapefile already has a .prj file associated with it the Name and Untits section will already be set and uneditable. If you wish to edit the projection you must delete the .prj file using Window Explorer.

Next click the Show Advanced Options check box if not already done.

Step 6. Click the Datum tab and choose NAD_1983_To_NAD_1927_NADCON from the Geographic Transformation dropdown list. Click Next>

Step 7. Choose the new Coordinate System Type, Name and Units. Click Next

Step 8. Choose a file location and name for the re-projected shapefile. Click next.

Step 9. Verify the new settings are correct and click Finish.

Step 10. After the shapefile is converted you will be promped to load the new shapefile in the View

 

Re-projecting Shapefiles in Common Pennsylvania Coordinate Systems

Common PA Coordinate Systems

DCNR

Map Projection Name: Lambert Conformal Conic
Standard Parallel: 33
Standard Parallel: 45
Longitude of Central Meridian : -78
Latitude of Projection Origin: 0.0
False Easting: 0.0
False Northing: 0.0
Planar Coordinate Encoding Method: Coordinate Pair
Planar Distance Units: meters
Horizontal Datum Name:North American Datum of 1927
Ellipsoid Name: Clarke 1866
Semi-major Axis: 6378206.4
Denominator of Flattening Ratio: 294.98

 

PADOT - PAGC

Map Projection Name: Geographic
Latitude_Resolution: 0.0002743
Longitude_Resolution: 0.0002743
Geographic_Coordinate_Units: Decimal degrees
Horizontal Datum Name:North American Datum of 1983
Ellipsoid Name: GRS80
Semi-major Axis: 6378137.0
Denominator of Flattening Ratio: 298.26

 

PAFBC

Map Projection Name: Albers_Conical_Equal_Area
Standard Parallel: 40
Standard Parallel: 42
Longitude of Central Meridian : -78
Latitude of Projection Origin: 390
False Easting: 0
False Northing: 0
Planar Coordinate Encoding Method:Coordinate Pair
Planar Distance Units: meters
Horizontal Datum Name: North American Datum of 1927
Ellipsoid Name: Clarke 1866
Semi-major Axis: 6378206.4
Denominator of Flattening Ratio: 294.98

 

PADEP - PSU ERRI

Map Projection Name:Albers_Conical_Equal_Area
Albers Conical Equal Area:
Standard Parallel:40
Standard Parallel:42
Longitude of Central Meridian :-78
Latitude of Projection Origin:39
False Easting:0
False Northing:0
Planar Coordinate Encoding Method:Coordinate Pair
Abscissa Resolution:100
Ordinate Resolution:100
Planar Distance Units:meters
Horizontal Datum Name:North American Datum of 1927
Ellipsoid Name:Clarke 1866
Semi-major Axis:6378206.4
Denominator of Flattening Ratio:294.98

 

Use the Parameters tab in the Projection Utility Wizard to set custom parameters.

Custom Coordinate Systems can be used with the Projector! Extension as well by using the Custom option.

BACK to USC GIS Page

 

 

Last Updated  6/16/05