WMS Tutorials Introduction – Images

v. 11.1

WMS 11.1 Tutorial

Introduction – Images
Import images in a variety of formats and register the images to a coordinate projection

Objectives
Import various types of image files from different sources. Learn how to work with online maps in the
WMS interface. Register the images to a real-world projection and save an image world file.

Prerequisite Tutorials Required Components Time

 None  Data  15–30 minutes
 Map

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1 Introduction ......................................................................................................................... 2
1.1 Getting Started ............................................................................................................. 2
2 Geotiff Files .......................................................................................................................... 3
2.1 Tiling Images ............................................................................................................... 3
3 Online Images ...................................................................................................................... 3
3.1 Getting Online Images ................................................................................................. 3
3.2 Exporting Images ......................................................................................................... 4
4 World Files........................................................................................................................... 5
5 Image Resolution ................................................................................................................. 6
6 Registering Scanned Images ............................................................................................... 6
6.1 Registering in Geographic Coordinates........................................................................ 8
6.2 Converting the Coordinates to UTM ............................................................................ 9
7 Conclusion.......................................................................................................................... 10

1 Introduction
Images are an important part of most projects developed using WMS. An image is
composed of pixels. The size and number of pixels in an image determines the level of
detail visible in the image.
WMS uses images to derive data such as roads, streams, confluences, land use, and soils,
as well as to provide a base map—or backdrop—to a watershed. Images must be
georeferenced in order to be useful in WMS. Georeferencing an image defines
appropriate x and y coordinates so that distances and areas computed from the image will
be accurate.
Because images are commonly used in Geographic Information System (GIS) programs
and modeling systems like WMS, data developers often store the georeferencing
information as either part of the image file (a GeoTIFF file for example), or in a separate
file commonly referred to as a “world” file.
This tutorial gives an overview of the primary ways to import and georeference (or
register) images in WMS. Using GeoTIFF files, online images, and world files will be
discussed and demonstrated. Image resolution and registering scanned images will also
be discussed and demonstrated.

1.1 Getting Started

To reset the data, display options, and other WMS settings to their defaults, do the
following:
1. If necessary, launch WMS.
2. If WMS is already running, Press Ctrl-N, or select File | New… to ensure that the
program settings are restored to their default state.
3. A dialog may appear asking to save changes. Click Don’t Save to clear all data.
The graphics window of WMS should refresh to show an empty space.

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2 GeoTIFF Files
GeoTIFF image files include georeferencing information. This means it is not necessary
to specify coordinates when images are read in because it is done automatically. Multiple
images can be tiled together and shown as a single image.

2.1 Tiling Images

1. Select File | Open… to bring up the Open dialog.
2. Browse to the images\images\ directory and select “redridge.TIF”.
3. Click Open to import the image and exit the Open dialog.
The image will appear in the Main Graphics Window and “ redridge.TIF” will appear
under the “ GIS Data” folder in the Project Explorer.
4. Click Open to bring up the Open dialog.
5. Select “josephspeak.TIF” and click Open to import the image and exit the Open
dialog.
A new map should appear adjacent to the “ redridge.TIF” image in the Graphics
Window. Notice that the adjacent images are geo-referenced. This can be determined by
the latitude and longitude information to the right of the cursor coordinates below the
Graphic Window.

3 Online Images
WMS has tools for loading various types of online images from the internet that are both
high-quality and seamless (they do not contain collars). Online images require an internet
connection. This tool uses a web map service to download and view various types of
images in the WMS graphics window. These images are pre-registered to the display
projection (or if no data exists, the projection is set to the image's native projection) and
more than one online image can be imported at a time.
The advantages of online images are that they are seamless, data is available throughout
the world, and that they can be reprojected to the display projection without needing to
georeference the image. The disadvantage of online images is that the image can take
longer to refresh when zooming or panning the display in the graphics window.

3.1 Getting Online Images

1. Click Get Online Maps at the top of the WMS window to bring up the Get
Online Maps dialog (Figure 1).
2. While pressing Ctrl, select World Imagery and USA Topo Maps (scroll to the
right to locate this one).
3. Click OK to close the Get Online Maps dialog and load the World Imagery and
USA Topo Maps online maps into WMS.
The process of loading the maps may take a few minutes.

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Figure 1 Get Online Maps dialog

Notice that the online images are imported and displayed based on the current screen
coordinates. Two new layers, “ World Imagery” and “ USA Topo Map” were
created in the Project Explorer under the “ GIS Data” folder.
4. Turn off “ World Imagery” under the “ GIS Data” folder in the Project
Explorer. Images can be turned on and off by unchecking the box next to the
image in the Project Explorer.
5. Zoom into various areas of the USA Topo Maps image and compare it with
the topographic map image imported earlier in this tutorial.
Notice that the display of the online images takes time to update when panning or
zooming in and out. The display takes time to update because WMS downloads an
updated image from the internet every time zooming in or framing the image. While the
image is downloading, it is possible to continue to work, but some or all of the current
view of the image may not be shown until the image is downloaded.
6. Frame the project.
This centers and redraws all the data in the graphics window so that all currently visible
objects fit and can be seen at once.
7. Turn on “ World Imagery” in the Project Explorer.

3.2 Exporting Images

Online images can be exported as static image files to the computer so the display
updates faster.
1. Right-click on “ World Imagery” in the Project Explorer and select
Export… to bring up the Resample and Export Raster dialog.
2. Enter “2.0” as the Resampling ratio.

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3. Turn on Add to project after saving.

4. Click OK to export the raster, close the Resample and Export Raster dialog, and
bring up the Save As dialog.
5. Select the desired destination folder.
It is recommended to save related files (those from a specific project) in the same
location. This ensures that needed files are easily found.
6. Select “GeoTIFF Files (*.tif)” from the Save as type drop-down.
7. Enter “Sample_exported_raster_world.tif” as the File name and click Save to
save the file and close the Save As dialog.
It may take a few minutes for WMS to download the higher-resolution image.
8. Repeat steps 1–7 for the USA Topo Maps online image, entering
“Sample_exported_raster_usatopo.tif” as the file name.
After the images have been downloaded, they will automatically open in the graphics
window and in the Project Explorer under “ GIS Data”.
9. Turn off both “ USA Topo Maps” and “ World Imagery” in the Project
Explorer.
10. Zoom in to various sections of the new images, and compare the images with
the topographic maps that were opened earlier in this tutorial.

4 World Files
Many image files do not contain georeferencing information. For example, JPEG files do
not have georeferencing tags in the file like GeoTIFF images have. Most organizations
that make images available also distribute world files containing the georeferencing
information along with the image files. These world files usually have the same name as
the corresponding TIFF or JPEG file, but with the extension “.tfw” for TIFF files and
“.jgw” or “.jpgw” for JPEG files. If downloading a world file and asked to supply a name
for it, follow this naming convention. Use the following procedure to open a JPEG file
and its corresponding georeferencing information in WMS:
1. Select File | New .
2. Click Don’t Save if asked to save changes.
3. Click Open to bring up the Open dialog.
4. Select “richfield1.jpg” image file and click Open to import the image and exit
the Open dialog.
Because there is a world file named “richfield1.jpgw” in the same folder as
“richfield1.jpg”, the image is automatically registered. If a world file for an image is not
named with the TFW extension (or JGW or JPGW extensions), there is an option to
import the world file from within the Registration dialog.
Properly georeferenced files overlap automatically, thereby avoiding tedious manual
tiling of the images). It is not necessary to be exact in obtaining images and files from a
source that distributes world files with images, as overlapping is not a problem.

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5. Repeat steps 3–4 for “richfield2.jpg” and “richfield3.jpg”.

Feel free to use Zoom and Pan and turn the different images on and off to explore
how they can be viewed and used when overlapping.
Imagery can also be obtained using the Get Data From Map or the Get Data Tool
tools in WMS.

5 Image Resolution
Images are usually available in different resolutions. In this part of the exercise, different
topographic maps showing the same area at different resolutions will be opened.
1. Select File | New .
2. Click Don’t Save if asked to save changes.
3. Select File | Open… to bring up the Open dialog.
4. Select “tm4m.jpg” and click Open to import the image and exit the Open dialog.
5. Zoom in on the image until the individual pixels of the image are visible.
6. Repeat steps 3–4 for “tm16m.jpg”.
7. Select Display | View | Previous View, or use the View Previous tool, to
switch back to the previous view.
8. In the Project Explorer, turn on and off “ tm16m.jpg” to see the difference in
resolution of the two images
Notice how much larger the individual pixels are in the “ tm16m.jpg” image.
9. Repeat steps 3–4 for “tm32m.jpg”.
10. Click View Previous to see the difference in resolution.
When zoomed in on the three images, as the map scale increased the map showed less
detail. “tm4m.jpg” shows much more detail than either “tm16m.jpg” or “tm32m.jpg”.
Images are commonly available on a scale of 1:24000, 1:100000, or 1:250000. 1:24000
maps cover far less area than 1:100000 or 1:250000 maps, but they show much more
detail (higher resolution). It would take thirty-two 1:24000 maps to cover the same area
that is covered by one 1:100000 map.
If great detail is needed for a watershed, use the 1:24000 maps. If the watershed is very
large, this size of map will provide too much detail. It would be difficult to see the big
picture of the watershed, and a 1:100000 or 1:250000 scale map may be more appropriate
in such a case.

6 Registering Scanned Images

It is not always possible to obtain a GeoTIFF image or an image with a world file. In
such cases, register the image manually. The coordinates— in a projected or geographic
system—of three points on the image must be known. Before scanning a paper image or

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downloading an image from the Internet, mark the three points in order to easily find
them when registering the image in WMS.
Here, a part of a soils file is used as a “scanned image”. This file will be used in a later
tutorial to develop a soils coverage and to compute a composite curve number.
1. Click New .
2. Click Don’t Save if asked to save changes.
3. Click Open to bring up the Open dialog.
4. Select “soils.tif” and click Open to exit the Open dialog and bring up the
Register Image dialog (Figure 2).

Figure 2 Register Image dialog

An image representing soil types will appear in the Register Image dialog. Three small
red X's are marked on the image. Near each red X is a plus sign with a number “1”, “2”,
or “3” by it.
5. Using the Zoom tool, zoom in over the area containing the red X and the plus
sign mark (+) labeled “1”.

6. Using the Register Points tool, drag the plus sign mark (+) labeled “1” over
the nearby X. Make sure that the plus sign is directly over the X.

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7. Click Frame to restore the image back to its original state.

8. Repeat steps 5–7 for the plus signs labeled “2” and “3”.

6.1 Registering in Geographic Coordinates

The three points are known in geographic coordinates, or latitude and longitude. They
will be registered that way, and then converted to UTM in the following section. Notice
that each longitude value is negative due to being west of the prime meridian.
1. For each point, enter the longitude and latitude from the table below into the
World Coordinates column under each point number.
Point #1 Point #2 Point #3

Longitude (X) -112.481944 -112.477222 -112.330277

Latitude (Y) 38.68500 38.57667 38.57611

2. When finished, click OK to close the Register Image dialog.

3. Frame the project.
With the coordinates entered, a slight rotation from true north may be seen which is
expected (Figure 3). It will be rectified later when the display projection is changed to a
UTM coordinate system. If the image appears distorted or extremely crooked, it’s
possible the coordinates were entered incorrectly or the plus sign marks (+) were placed
inaccurately.
4. To make adjustments, right-click on “ soils.tif” in the Project Explorer and
select Register Image… to bring up the Register Image dialog.
5. Make the needed adjustments to the position of the plus marks over the red Xs
and verify the coordinates as shown in the table above.
6. Click OK when done to close the Register Image dialog.

Figure 3 Slight rotation from true north visible

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6.2 Converting the Coordinates to UTM

Geographic coordinates are commonly used on maps because they provide a global
reference for any point in the world. For engineering work, a planimetric system is
necessary. The Universal Transverse Mercator (UTM) projection is commonly used so
the coordinate system that the image file is currently in (Geographic) will be specified
and the display projection will be set to UTM to work in that projection.
1. Right-click on the “soils.tif” image in the Project Explorer and select Projection |
Projection… to bring up the Projection dialog.
2. In the Horizontal section, select Global projection.
3. The Horizontal Projection dialog may appear automatically, if it does not, click
Set Projection… to bring up the Horizontal Projection dialog.
4. In the Filter strings edit field, type “Geographic NAD 1983”.
5. Select “Geographic Coordinate Systems | North America | NAD 1983” from the
tree window at the top of the dialog.
6. Click OK to close the Horizontal Projection dialog.
7. Click OK to close the Projection dialog.
8. Select OK on the message about changing the projection of a raster. The Save As
dialog will appear.
9. Enter “soils_exported.tif” as the File name and click Save.
10. Click OK at the warning message stating the display projection needs to be set.
The Display Projections dialog will appear. If the dialog does not appear, right-
click on “ soils_exported.tif” to bring up the Display Projections dialog.
The projection that the soils image file is in (Geographic) has been set correctly. The
display projection will be set to UTM to make it the working projection.
11. In the Horizontal section, select Global projection and click Set Projection… to
bring up the Horizontal Projection dialog.
12. In the Filter strings edit field, type “UTM Zone 12”.
13. Select “Projected Coordinate Systems | UTM | NAD 1983 | NAD 1983 UTM
Zone 12N” from the tree window at the top of the dialog.
14. Click OK to close the Horizontal Projection dialog.
15. In the Vertical section, “Meters” should be selected from the Units drop-down.
(The Datum and Units area in the Vertical section will be set according to the
assigned projection.)
16. Click OK to close the Display Projection dialog.
17. Frame the project
The original image object projection is still set to geographic and has not been changed,
but the display of the image in the WMS display window has changed from geographic to
UTM. Now, any measurements taken or data created from the image will have meters for
coordinate values.

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7 Conclusion
This concludes the WMS “Introduction – Images” tutorial. The following key concepts
were discussed and demonstrated:
 How to use GeoTIFF files.
 How to use online images.
 How to use world files.
 Image resolution.
 How to register images.

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