map projection using arcgis - texas a&m university · brief overview of map projection using...

18
Texas A&M University Department of Civil Engineering Map Projection Using ArcGIS Francisco Olivera, Ph.D., P.E. Srikanth Koka Lauren Walker Aishwarya Vijaykumar Department of Civil Engineering Texas A&M University December 5, 2011 Contents Brief Overview of Map Projection Using ArcGIS ............................................................................. 1 Goals of the Exercise ....................................................................................................................... 2 Computer and Data Requirements ................................................................................................. 2 Procedure ........................................................................................................................................ 2 1. Projections of the World ..................................................................................................... 2 A. View of the world in geographic coordinates (longitude and latitude) .......................... 2 B. View of the world in Robinson Projection ....................................................................... 4 C. View of the world “from space” ...................................................................................... 6 2. Projections of the United States.......................................................................................... 7 A. View of the United States in geographic coordinates ..................................................... 7 B. View of the United States in Albers Equal Area projection ............................................. 8 3. Projections of Texas............................................................................................................. 9 A. View of Texas in geographic coordinates ........................................................................ 9 B. View of Texas in Lambert Conformal Conic projection ................................................. 11 C. View of Texas in the Texas Centric Mapping System (TSMS) ........................................ 12 4. Defining the Projection...................................................................................................... 14 5. Projecting Data Using ArcToolBox ..................................................................................... 17 Brief Overview of Map Projection Using ArcGIS Map projection involves transforming spatial data defined on the curved surface of the earth to the flat surface of a map. A map projection is the mathematical algorithm used for this transformation. ArcToolBox allows the transformation of data from one map projection to another.

Upload: hoangdang

Post on 02-Jul-2018

227 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering

Map Projection Using ArcGIS

Francisco Olivera, Ph.D., P.E.

Srikanth Koka

Lauren Walker

Aishwarya Vijaykumar

Department of Civil Engineering

Texas A&M University

December 5, 2011

Contents Brief Overview of Map Projection Using ArcGIS ............................................................................. 1

Goals of the Exercise ....................................................................................................................... 2

Computer and Data Requirements ................................................................................................. 2

Procedure ........................................................................................................................................ 2

1. Projections of the World ..................................................................................................... 2

A. View of the world in geographic coordinates (longitude and latitude) .......................... 2

B. View of the world in Robinson Projection ....................................................................... 4

C. View of the world “from space” ...................................................................................... 6

2. Projections of the United States.......................................................................................... 7

A. View of the United States in geographic coordinates ..................................................... 7

B. View of the United States in Albers Equal Area projection ............................................. 8

3. Projections of Texas............................................................................................................. 9

A. View of Texas in geographic coordinates ........................................................................ 9

B. View of Texas in Lambert Conformal Conic projection ................................................. 11

C. View of Texas in the Texas Centric Mapping System (TSMS) ........................................ 12

4. Defining the Projection ...................................................................................................... 14

5. Projecting Data Using ArcToolBox ..................................................................................... 17

Brief Overview of Map Projection Using ArcGIS

Map projection involves transforming spatial data defined on the curved surface of the earth to

the flat surface of a map. A map projection is the mathematical algorithm used for this

transformation. ArcToolBox allows the transformation of data from one map projection to

another.

Page 2: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 2

Goals of the Exercise This exercise will introduce you to the procedure for projecting GIS data in ArcGIS.

Computer and Data Requirements This exercise has been completed using ArcGIS 10. All the data needed for this exercise are

contained in the MapProj.mdb geodatabase. Download the MapProj.zip file containing the

geodatabase from the class website. Unzip it and save the files to a working directory in your

computer.

Procedure

1. Projections of the World

A. View of the world in geographic coordinates (longitude and latitude) (1) Open a new ArcMap document. Add data to your map, using the Add Data button

and browse to the MapProj.mdb geodatabase in your working directory.

(2) Double click on the geodatabase to access the feature classes inside it. Select the

cntry94 and world30 feature classes while holding down the Ctrl key, and then click

Add. Make sure that world30 is below cntry94 in the Table of Contents.

(3) To show just the outlines of the features in the world30 layer, click on the symbol for

world30 in the Table of Contents. On the left hand side of the Symbol Selector window

that opens, you can see a list of color schemes; select the one named Hollow, and

then click OK. You can now see the world map in geographic coordinates.

(4) To label the countries, right-click on the cntry94 layer and select the Label Features

option in the dropdown menu. To customize the label display, right click on the layer,

and then click on Properties/Labels. To remove the labels, unselect the Label Features

in this layer option and click OK.

Page 3: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 3

(5) To label a few selected countries, first display the Draw toolbar in ArcMap. Click on

Customize/Toolbars/Draw to add it to the map.

(6) On the Draw toolbar, click the down-arrow beside the New Text button , and

select the Label option .

(7) In the Labeling Options, choose the Placement and Label Style of your preference and

close the form. Click on the countries you want to label. Save the project as

World.mxd.

Page 4: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 4

Move the cursor around on the view and you will see a pair of numbers to the bottom right

of the ArcMap window. These numbers are the coordinates of the cursor and from the

values displayed in the bottom right part of the screen you can see that they are displayed

in the degrees minutes format in decimal degrees and are the latitude and longitude of the

cursor location.

B. View of the world in Robinson Projection

The map projections of cntry94 and world30 are geographic; however, they can be viewed

in different projection systems. A common projection system for the world is the Robinson

projection.

(1) Create a new data frame in ArcMap using Insert/Data Frame. Add the world30 and

cntry94 feature classes to this new data frame by right-clicking on New Data Frame

and selecting Add Data or from the File dropdown menu.

(2) Again, rearrange the layers and change the legend of world30 as explained in the

previous section. To view the world in Robinson projection, right click on the new data

frame and click on Properties/Coordinate System.

(3) In the Select a Coordinate System box, click on Predefined/Projected Coordinate

System/World/Robinson (World) and then click OK.

Page 5: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 5

(4) Click Yes on the warning message that appears. You will see the world in the Robinson

projection. Refresh the map by clicking on the Full Extent tool , and then save the

document.

The Robinson projection is a world map projection designed to present the whole earth with

minimum distortion at any location. If you move the cursor over this space, you should see

that the coordinates are now in meters instead of decimal degrees in the projected

coordinate system.

Page 6: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 6

C. View of the world “from space”

(1) Create a new data frame and add the world30 and cntry94 feature classes to it. Again,

rearrange the layers and change the symbol color if necessary.

(2) To view the world “from space,” change the data frame coordinate system to

Predefined/Projected Coordinate System/World/The World from the Space and

select OK. As before, a warning message appears where you should select Yes. Refresh

the map by clicking on the Full Extent tool, and then save the document.

Page 7: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 7

2. Projections of the United States

A. View of the United States in geographic coordinates

(1) Create a New Empty Map file and save it as USA.mxd.

(2) Add the states and latlong feature classes to the data frame. These data are polygons

of the states of the United States and lines forming a 5-degree grid of latitude and

longitude.

(3) Click on the Zoom In tool and zoom into the contiguous United States. If

necessary, use the Pan tool to move the map to the center of the window.

Page 8: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 8

B. View of the United States in Albers Equal Area projection

The Albers Equal Area projection has the property that the area bounded by any pair of

parallels and meridians is exactly reproduced. While the projection preserves the correct

area, it somewhat distorts the direction, distance and shape.

(1) Insert a new data frame and add states and latlong. Zoom into the the contiguous

United States.

(2) To view the United States in Albers Equal Area projection, right-click on the data frame

and click on Properties/Coordinate System. In the Select a coordinate system box,

click on Predefined/Projected Coordinate System/Continental/North

America/USA_Contiguous_Albers_Equal_Area_ Conic and click OK. Choose Yes if a

warning box appears. Save your document.

Zoom in and compare the shape of the United States in geographic coordinates and in

Albers projection. You can see that in geographic coordinates the United States appears to

be wider and flatter than it does in Albers Equal-Area Projection. This effect occurs because

as you go northward, the meridians converge toward one another while the successive

parallels remain parallel to one another. When you reach the North Pole, the meridians

converge completely.

Page 9: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 9

In Albers projection, the square boxes of latitude-longitude appear as elongated

quadrilaterals with a bottom edge longer than their top edge. In geographic coordinates, the

effect of the real convergence of the meridians is lost because the latitude and longitude

grid form a set of perpendicular lines, which is what makes the United States seem wider

and flatter in geographic coordinates.

3. Projections of Texas

A. View of Texas in geographic coordinates

(1) Create a New Empty Map file and save it as Texas.mxd.

(2) Add the counties and latlong feature classes to the data frame, and rearrange the

layers and change the symbol colors if necessary.

Since we are concerned only about Texas, it is only necessary to make the Texas counties

visible.

(3) Right click on the Counties layer and then click on Properties/Symbology. In the Show

box, click on Categories/Unique Values. In the Value Field box, select State_Name.

Page 10: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 10

(4) Click the Add Values button. Click on Complete List. Then, click on Texas, the Add to

List button, and then on OK. Uncheck the <all other values> box. Click Ok.

(5) Zoom into the Texas part using the Zoom In tool. The latitude and longitude grid

displayed is at 5-degree intervals. You can determine what latitude or longitude a

particular line represents by moving the cursor to any line and read its value on the

right corner of the tool bar.

Page 11: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 11

B. View of Texas in Lambert Conformal Conic projection

The Lambert Conformal Conic projection is a standard projection for presenting maps of

land areas whose East-West extent is large compared with their North-South extent. This

projection is “conformal” in the sense that lines of latitude and longitude, which are

perpendicular to one another on the earth’s surface, are also perpendicular to one another

in the projected domain.

(1) Insert a new data frame and add counties and latlong data. Follow previous directions

to select to view only Texas.

(2) To view Texas in Lambert Conformal Conic projection, right-click on the data frame

and click on Properties/Coordinate system. In Select Coordinate System box, click on

Predefined/Projected Coordinate System/ Continental/ North

America/USA_Contiguous_Lambert_Conformal_Conic, then OK.

If necessary, select Yes in the warning message box. After clicking the Full Extent button, it

can be seen that the meridians converge to a point. Make sure that you are only viewing

Texas counties by following the steps that were outlined previously in Part A.

After zooming in to Texas with the Zoom-In tool, a more familiar shape of Texas can be seen.

Page 12: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 12

Notice that Texas appears to be tilted to the right slightly. This occurs because the Central

Meridian of the projection used is 96ºW, which would appear as a vertical line in the display

if it were shown. Regions to the west of this meridian (most of Texas) appear tilted to the

right while those to the east of this meridian appear tilted to the left.

C. View of Texas in the Texas Centric Mapping System (TSMS)

In order to present a more pleasing map of Texas, and to minimize distortion of distance in

statewide maps, the Texas Department of Information Resources has approved two

standard projections of Texas called Texas Centric Mapping System (TSMS)

(http://www.dir.state.tx.us/tgic/committee/stnd/draft-rule-2001.pdf). One of them is

Albers Equal Area and the other Lambert Conformal Conic. Their definition is:

Projection: Albers Equal Area (or Lambert Conformal Conic)

Datum: North American Datum of 1983 (NAD83)

Ellipsoid: Geodetic Reference System of 1980 (GRS80)

Map units: meters

Central Meridian: 100°W (-100.0000)

Reference Latitude: 18° N (18.000000)

Standard Parallel 1: 27° 30' N (27.500000)

Standard Parallel 2: 35° N (35.000000)

False Easting: 1500000

False Northing: 6000000 (or 5000000 for Albers Equal Area)

This means that the standard parallels, where the cone cuts the earth's surface, are located

at about 1/6 of the distance from the top and bottom of the State, respectively, and that the

Page 13: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 13

origin of the coordinate system (at the intersection of the Central Meridian and the

Reference Latitude) is in the center of the State, to which the coordinates (x, y) = (1500000,

6000000) meters is assigned, so that the (x, y) coordinates of all locations in the State are

positive.

(1) Insert a new data frame and add counties and latlong layers as done previously.

(2) Right-click on the data frame and click on Properties/Coordinate system. In the Select

Coordinate System box, click on Custom and then on New/Projected Coordinate

System button.

(3) Enter the map projection information given above as shown below. In the Geographic

Coordinate System box, click Select and in the Browse for Coordinate System window

click on North America/North American Datum 1983.prj/Add. Then click OK button to

finish projecting the data frame.

Zoom into the Texas part using Zoom In tool. (Make sure you are only viewing Texas

counties by following the steps in Part A.)

Page 14: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 14

4. Defining the Projection

Every dataset is either in a geographic coordinate system or in a projected coordinate system.

ArcMap cannot determine what projection a dataset is in unless and until it is specified. For

shapefiles, this information is stored in a file with extension prj. Geodatabases store it as a table

within the database. Even though a dataset might have a coordinate system, the corresponding

projection information might be missing. In this case, the information has to be obtained from

the data source and the projection should be defined.

If you add a layer to a data frame and its projection information is missing, you will get the

following message:

This is not a problem for displaying data as long as ArcMap does not need to project it on-the-

fly.

Page 15: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 15

In this part of the exercise, you are going to define the projection information of the STATSGO

(State soil geographic dataset) data of Texas. This dataset contains soils information for the state

of Texas, but its spatial reference properties are not defined. So, the information has to be

obtained from the host of the data. The dataset was obtained from the United States

Department of Agriculture (USDA).

(1) Before defining the projection, open a new ArcMap document, and add quad and

STATSGO to the data frame. You will see the above-mentioned warning message and

you will observe that both the layers do not overlay upon one another. This is because

ArcMap does not know the projection details of STATSGO.

(2) Close the document because you cannot define the projection of STATSGO in

ArcCatalog if ArcMap is using it.

Listed below are the values that will be used to define the projection.

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Planar:

Map_Projection:

Map_Projection_Name:

Albers_Conical_Equal_Area:

Standard_Parallel: 29.50

Standard_Parallel: 45.50

Longitude_of_Central_Meridian: -96.0

Latitude_of_Projection_Origin: 23.0

False_Easting: 0.0

False_Northing: 0.0

Planar_Coordinate_Information:

Planar_Coordinate_Encoding_Method: coordinate pair

Coordinate_Representation:

Abscissa_Resolution: 6.35

Ordinate_Resolution: 6.35

Planar_Distance_Units: meters

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1927

Ellipsoid_Name: Clarke 1866

Semi-major_Axis: 6378206.4

Denominator_of_Flattening_Ratio: 294.9786982

Page 16: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 16

Though projection for datasets can be defined either with ArcCatalog or ArcToolBox, we will use

ArcCatalog in this exercise.

(3) In ArcCatalog, browse down to the geodatabase, open the geodatabase, right-click on

the STATSGO feature class and then click on Properties.

(4) In the Feature Class Properties wizard that opens, click on the XY Coordinate System

tab. You can see here that the XY Coordinate System for this feature class is

‘unknown’.

(5) Click on Select…A new window titled Browse for Coordinate System opens. Double-

click on Projected Coordinate Systems/Continental/North America/ USA Contiguous

Albers Equal Area Conic. Click Add.

(6) Click Apply and then click OK.

(7) Again, open a new ArcMap document and add the Quad and STATSGO layers. This

time you should not see the warning message and you will see the layers overlay one

upon another.

(8) To clearly see the layers, make sure that the first layer is STATSGO and the second is

quad. Change the symbol color of STATSGO and make it transparent (hollow).

(9) Do this by clicking on the square below the layer name and then select Hollow in the

Symbol Selector Wizard. Your map should look similar to the image below.

Page 17: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 17

5. Projecting Data Using ArcToolBox

Data in one projection can be transformed into another projection. It is very useful for all the

data layers to be one projection when they refer to the same spatial extent.

(1) Before going onto changing the projection of STATSGO, in ArcMap start ArcToolBox by

clicking on the red toolbox icon on the toolbar.

(2) Click on Data Management Tools/Projections and Transformations: Click on

Feature/Project.

(3) Click on the folder icon located to the right of the Input Dataset or Feature Class.

Browse to the folder where MapProj.mdb is located. Double-click on the geodatabase

to see all the feature classes inside it.

(4) Select the STATSGO feature class and click on the Add button to choose the feature

class that is to be projected.

(5) Select the folder icon to the right of Output Coordinate System. In the Spatial

Reference Properties wizard, click on Select.

(6) In the Browse for Coordinate System dialog box, click on Projected Coordinate

Systems/Continental/North America/USA Contiguous Lambert Conformal Conic, click

Add, and then click Apply/OK. Click OK and the program will begin to execute the

projection.

Page 18: Map Projection Using ArcGIS - Texas A&M University · Brief Overview of Map Projection Using ArcGIS ... 6 2. Projections of the ... This exercise has been completed using ArcGIS 10

Texas A&M University

Department of Civil Engineering 18

(7) To verify if the dataset is projected properly or not, open a new ArcMap document and

add quad and STATSGO_Lambert to its data frame. If it has been projected properly,

then they should overlap.

One more thing that should be noted is the capability of ArcMap to project data on-the-fly.

Try to see the spatial reference properties of the two layers in the map by right-clicking on

each of them and then clicking on the Properties, then on Source tab in the Layer

properties wizard.

These materials may be used for research and educational purposes only. Please credit the

authors and the Department of Civil Engineering, Texas A&M University.

All commercial rights reserved. Copyright 2011: Texas A&M University.