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Validating Georeferencing in Geographic Imager

When georeferencing a map in Geographic Imager, there are two tools which can be used to check spatial accuracy: Validate and Show Image Extents Online. With Validate, click a point on the image and it will show the corresponding location on the web map service so that you can compare the difference between them. Show Image Extents Online will display a rectangle representing the spatial extent of the image on the web map.

The image below shows the Validate tool in action. Selecting the tool and clicking on the road intersection brings up the same intersection in the web map, displaying how accurate the georeferencing may be. It is good practice to test several known points on the image. Choose features that will be easy to identify on the web map such as road intersections, coastlines, buildings, and landmarks.

The Show Image Extents Online tool is shown in the image below. Use this tool to see the full area covered by the image. Note that the rectangle shown on the web map will include the non-map areas of the page (borders, legend, etc).

 

Avenza Systems Fixed and Floating License Solutions: What Are The Differences?

Avenza desktop applications, MAPublisher and Geographic Imager offer two options for the licensing system: Fixed license and Floating license.

The Fixed license option allows only one license per computer. For most users or small companies, this is generally sufficient, even with a few licenses. Since your license is fixed to a specific computer, it can’t be moved freely to another machine. However, Avenza does allow you to move your license occasionally. For example, if you purchased a new computer or when your computer is being fixed and you need to transfer your fixed license to another computer. If your subscription status for MMP (MAPublisher Maintenance Program) or GMP (Geographic Imager Maintenance Program) is up-to-date, then moving your fixed license to another computer (i.e. rehosting a license) can be done without a cost. Complete this form to do so. You will receive a notification email from Avenza when this is completed.

The Floating license option is for users who wants to share a number of licenses on the network. This is a great solution for any size company that has multiple users who share use of MAPublisher or Geographic Imager. You will need to set up a license server for which users will need check out a license from the server before using MAPublisher or Geographic Imager. In general, this option is used when sharing a number of license with colleagues. For example, the license server holds two seats of MAPublisher license. When users on Computer A and Computer B are using MAPublisher, other users can’t check out a license until the borrowed licenses are checked in.

An example environment of a floating license system

Another great advantage of the floating license the ability to borrow a roaming license with their laptop so that they can use MAPublisher and Geographic Imager outside their immediate office. This is a good solution for users who need to use the software on the go and doesn’t have a connection to the floating license server.

For more information about the licensing options for our MAPublisher and Geographic Imager, contact Avenza sales.

If you have any technical questions about setting up a license server or any other licensing issues, contact Avenza Technical Support.

Working With Avenza Floating Licenses Outside of Your Work Network

If you or your organization have a floating license for MAPublisher or Geographic Imager, this blog post is for you. Having a floating license provides you with a lot of flexibility when you want to bring your laptop computer outside your work network and use MAPublisher and Georaphic Imager at home or in the field.

Let’s say you have a laptop computer and you want to work on your mapping project outside your office network. You can do it if your organization has a floating license.

Step 1: Make sure all the software is installed

On your laptop computer, make sure that you have MAPublisher for Adobe Illustrator or Geographic Imager for Adobe Photoshop installed and that there is a valid floating license (for one or each product).

Step 2: Connect your laptop to the network and to the licensing server

If you are not sure how to connect your laptop to the network and to the server, please contact your IT administrator. It is essential that your laptop computer is connected to the license server so that you can obtain a liecnse from it.

Step 3: Follow the steps in the MAPublisher/Geographic Imager license management window

Open the License Management dialog box.

If you’re using MAPublisher, access MAPublisher by going to Help > MAPublisher Licensing > License Management.

If you’re using Geographic Imager, access License Management by going to File > Automate > Geographic Imager: License Management.

Click the Floating button to open the Floating License Setup dialog box.

Make sure that the “Allow roaming licenses” option is selected. Click OK.

Allow roaming licenses

Click the “Use roaming license” option and specify the number of days in the Duration of borrow option. This indicates how long you want to use the license outside of your network.

Specify duration of borrow

Clicking the “Checkout” button will change the status of the license. In this example, we borrowed a license from the license server for two days (December 16, 2015 starting date).

Checkout the license

Now you will be able to use your MAPublisher or Geographic license when your computer is disconnected from your work network.  You might want to test it by closing Adobe Illustrator or Photoshop, disconnect your computer from the network, restart Adobe Illustrator or Photoshop, and see if you can use MAPublisher or Geographic Imager.

Improve Mosaic By Resampling Images in Geographic Imager

The Mosaic function in Geographic Imager merges multiple georeferenced images together to create a single composite georeferenced image. Though the goal of the mosaic is to create a single and seamless composite image, combining images with the Mosaic tool will often result in a slight shift of the imagery due to differences in the original pixel registration grid. This means that even when images are in the same coordinate system with the same spatial resolution, error can still be introduced because of a difference in the pixel alignment. Due to this, mosaicking processes in general tend to produce results that may be very close, but not exact. With this in mind, the results of your mosaic may be improved by resampling your images beforehand to the smallest unit of the resolution.

As an example, let’s say we have an image where the pixel size is 2.00 metres. When plotting the X coordinates of every pixel in this image (using the top left corner of the pixel), the X coordinate value will be incremented by the number/distance of the pixel size. For example, if the X coordinate values were to start at 111.00, then the next pixel would be 113.00, 115.00, 117.00, and so on. It’s important to note that these coordinate values are discrete, which means that the values could not be 113.22 or 115.77 because the origin of the coordinate in this case starts at 111.00 metres.

Now, we have another image that we want to mosaic with the first image. In this instance, the first image will be “Image A” and the second image will be “Image B”. Image B has the same coordinate system as well as the same pixel size as Image A.

Take a look at the X coordinates in Image A and Image B below:

We can see that the X coordinate in the top-left corner is different between these two images, and as previously mentioned, we know that the X coordinate values are discrete. When mosaicking Image B to Image A, the X coordinate cannot be 111.75 or 113.75. The coordinates must be 111.00, 113.00, 115.00, and so on, following the pattern of the pixel grid values in Image A.

This means that Image B will need to be “shifted” or “snapped” to the closest coordinates when the mosaic is performed, see below:

As a result, the X coordinate of Image B will be shifted by 0.75 metres (less than half a pixel). The pixel with X coordinate 111.75 is now placed at 111.00 and the next pixel with X coordinate of 113.75 will now be placed at 113.00, and so on.

With this in mind, the results of your mosaic may be improved by resampling your images to the “smallest unit of the resolution”. The smallest unit of the resolution can be determined from the difference in the coordinates (spatial alignment difference) between the two images.

Looking back at our example, we can see that the smallest unit of the resolution (represented by the blue arrow) in this case is 0.75 metres – this is the value we will use to resample our images.

Once the images have been resampled to 0.75 metres, we may go ahead with our mosaic.

The above example demonstrates the possibility of a pixel shift after a mosaic for two images with a different pixel alignment. It should be noted that this example explains the problem in one-dimension (looking at only the X coordinate) when the image in reality is in two-dimension (looking at both X and Y coordinates). The basic principal of the pixel shift in 2D is the same, but it would include the direction of the shift when mosaicking images. In addition, it’s important to keep in mind that although resampling your images to the smallest unit of the resolution will improve the final mosaic, this is not always an efficient process when mosaicking with more than two images. Another thing to remember is that resampling your images will make your file size much larger. However, in cases where high precision is desired, resampling the images beforehand is a process that should be considered.

Creating a Super Overlay in Google Earth Pro

Our friends in the map library at Brock University in St. Catherines, Ontario have put together a very nice how-to on creating super overlays for Google Earth using Geographic Imager and Adobe Photoshop.

These instructions describe the process of georeferencing a high-resolution image, creating a geotiff file, using Google Earth Pro to make a super overlay and how to provide access to others. The full process is outlined here https://www.brocku.ca/maplibrary/Instruction/Creating_a_super_overlay.pdf

The Brock University Map Library can be contacted at maplib@brocku.ca

Geospatial PDF in Adobe Acrobat: Examining latitude and longitude values

After creating a map with MAPublisher or Geographic Imager, you might want to export it as a geospatial PDF file. You want to ensure that the georeference information of your Geospatial PDF files are correct before bringing them into the field for use. A great way to use geospatial PDF maps (and GeoTIFFs) is to load them onto an iPhone, iPad, or iPod touch with PDF Maps installed.

One way to check for georeference accuracy of geospatial PDF files is to use Adobe Acrobat. Open the “Analysis” tool from View > Tools > Analyze.

Adobe Acrobat: Opening Anlysis Tool

Click the “Geospatial Location Tool” from the Analyze panel.

With the Geospatial Location Tool enabled, you can see the latitude and longitude values of the map while you move the mouse over the opened Geospatial PDF file.

Geospatial PDF viewed in Adobe Acrobat

An important tip you should keep in mind: you need to set the preference option for this tool correctly depending on the coordinate system of the map in the geospatial PDF file.

Open the Preference dialog window:

Acrobat X on Windows: Edit > Preferences > General …
Acrobat X on Mac: Acrobat > Preferences …

In the Preference dialog window, find the preference category “Measuring (Geo)” from the list of categories.

Adobe Acrobat Preference dialog window

In the “Measuring (Geo)” category, take a look at the right side. There are many options for the georeferencing tool. One of the options is “Latitude and Longitude Format”. In this section, you have a checkbox option “Always display latitude and longitude as WGS 1984”.

Adobe Acrobat Preference option for Latitude Longitude Display

This option is very important. If the coordinate system of the map is “NAD 27 / UTM Zone 16 N”, which geodetic system would you like to have to show the latitude and longitude values in Adobe Acrobat? For example, if you are checking the latitude and longitude values in the WGS 1984 geodetic system, you should keep this option selected. However, if you are checking the latitude and longitude values in NAD 1927 geodetic system, then you should de-select this option. The difference in the distance at the same spot between two different geodetic systems may be small or large. If you would like to see the correct latitude and longitude values, you should be aware of this option.

3D Terrain Model using Geographic Imager

We created a video to show that it is possible to use geospatial data and the 3D capabilities of Adobe Photoshop. It performs very well with a decent computer and video card.

In this video, a combination of Geographic Imager and Adobe Photoshop functions are used to open a DEM file using a script. The script also transforms a DEM into a 3D model and allows for an overlay of a colour model based on the data or a custom image (e.g. ortho image). Video after the jump.

 

How to Create a 3D Rendition of a DEM With a Draped Image

NOTE: Prior to performing these steps with your data you would want to ensure that the DEM and image have the same geographic extents.

Item 2: Coordinate system of the map

Using Geographic Imager, open your DEM file and set the desired schema type. In this case the DEM was “Auto stretched”.

Item 2: Coordinate system of the map

With the DEM now opened and rendered as a 16-bit grayscale Image we can now make use of a number of Adobe Photshop tools to render it in 3D and to drape the image.

Item 2: Coordinate system of the map

The following steps will outline the Adobe Photoshop procedures required to create the 3D rendition:

1. Create a 3D mesh: Under the 3D menu within Photoshop select “New Mesh From Grayscle->Plane”

Item 2: Coordinate system of the map

2. We then use the “3D Object Rotate Tool” located in the Photoshop toolbar to manually rotate the mesh tilting it backwards, resulting in something like this

Item 2: Coordinate system of the map

3. The resulting mesh is too exaggerated for a realistic rendering of the landscape so we will adjust the y orientation of it using the “3D Object Scale tool” setting the Y: scale to 0.10

Item 2: Coordinate system of the map

This is the image after vertically rescaling it

Item 2: Coordinate system of the map

4.Once the 3D mesh has been rescaled the image can be draped

In the Adobe Photoshop “3D Materials” panel, click the “Edit Diffuse texture” button (as denoted in the screenshot below) and select the “Load Texture” option. Now locate and select the image you wish to drape on the 3D mesh.

Item 2: Coordinate system of the map

5. Within the Layers panel turn off the visibility of the Rocky Mountain DEM (as in the screenshot below).

Item 2: Coordinate system of the map

The end result should be a 3D model such as this.

Item 2: Coordinate system of the map

Georeferencing an Image in Adobe Photoshop with Geographic Imager

Today's topic: making an image georeferenced

As of Geographic Imager 5.0, there’s an updated workflow for georeferencing images. Learn more about Georeferencing and work through the tutorial.

 


Nowadays, it’s common to find great orthophotos and satellite imagery on the Web. However, after downloading these (sometimes) large files, you might find that some don’t have any georeferencing. Most likely these files are in an image format supported by Adobe Photoshop(e.g. JPG or TIF) and you can georeference it using the Geographic Imager Georeference tool.

These are the requirements to georeference an image:

  1. Knowing the coordinate system of the image (e.g. Mercator projection, State Plane system Alabama East, UTM system NAD 83 Zone 17 N..etc)
  2. Finding three or more points from the image to assign coordinate values to each of them. These points are known as ground control points.

The first thing you need to know is the coordinate system or projection of the image you are georereferncing. If you are unsure about which coordinate system the image uses, contact the data provider or search the metadata of the image on the Internet. If you cannot get the information of the coordinate system assigned to the image, you might want to try georeferencing with different coordinate systems to make the map as precise as possible.

The second requirement is working with the ground control points. One ground control point consists of several values: 1) Pixel X coordinate, 2) Pixel Y coordinate, 3) Ground X coordinate (e.g. longitude), and 4) Ground Y coordinate (e.g. latitude). Furthermore, to make georeferencing easier, ground control points must be clearly identifiable in the image. Cultural features such as road intersection, a sharp corner of a lot or boundary are good examples of locations used as ground control points.

Now that you know what you’ll need, we’ll demonstrate a georeference workflow using the Geographic Imager Georeference tool and Google Earth.

Step 1: Obtain a non-georeferenced image

This image is in JPEG format and there is no georeference information associated with it. In order to transform it to another coordinate system or projection, mosaic with other images, or align the image to vector work using MAPublisher for Adobe Illustrator, the image must first be georeferenced.

An example image collected

Step 2: Obtain the required information

As indicated above, two key pieces of information are required to georeference an image: a) the coordinate system of the image and b) defining ground control points

a) The coordinate system of the image

The image, collected from Google Earth, is projected in a coordinate system called WGS84 / Pseudo Mercator (this projection is common to Web based mapping systems and is also known as Web Mercator or Google projection).

b) Defining ground control points

We’ll need to define at least three ground control points for georeferencing. Below are the steps for finding out one of the ground control points.

On the non-georeferenced image, decide which spot to use as a point of reference. It should be available on Google Earth where you’ll find the X,Y coordinate values. For the first point, we’ll use the corner boundary between the pavement and a golf course.

a ground control point selected on my image

Using Google Earth, find the exact same spot as the one decided in the non-georeferenced image. Place a point symbol to help identify the coordinate values. Record the collected latitude and longitude values. The latitude and longitude values are at the centre of the point symbol symbol in the Google Earth window.

collecting the latitude and longitude values from Google Earth

Find the coordinates of two additional ground control points. The latitude and longitude values are in decimal degree format and the coordinate system of those values are in the geodetic system “WGS84”.

collected three ground control points

Step 3: Georeference in Geographic Imager

In Geographic Imager, click the Georeference tool button Geographic Imager: Georeference in the Geograhpic Imager main panel (or choose File > Automate > Geographic Imager : Georerence). The Georeference dialog box will open.

Geographic Imager: Georeference window

First, we’ll need to set the proper image coordinate system and input coordinate system (the information from Step 2a). In the Format section, click the blue “Specify” link to open the Input Format dialog box.

Georeference: Input

Here we’ll specify two parameters: Image Coordinate System and alternate input coordinate system. The image of the coordinate system is WGS84 / Pseudo-Mercator as found at Step 2a. Click the “Specify” button to find the coordinate system from the coordinate systems list.

The option “Use alternate input coordinate system” will not have to be selected if the X,Y coordinate values are collected in the Eastings/Northings in the WGS84 / Pseudo-Mercator coordinate system. When those latitude and longitude values are collected, those values are collected in the decimal degree format and the values are in degree in WGS84. We will use those latitude and longitude values for the georeferencing. Specify the destination coordinate system as WGS84.

When the settings are made, click OK to close the Input Format dialog box. All the selected coordinate system for each setting will be indicated in the Format section of the Georeference dialog box.

Georeference : Input image coordinate system and input coordinate system

The next step is to enter the three ground control points collected from Google Earth. Click the pencil tool at the top of the Georeference dialog box and click a point for one of the ground control points collected at the previous steps Georeference : Pencil tool.

a ground control point selected on my image

As soon as one point is clicked on the preview image, it will add one row in the Georeference table. This row contains the point name, PX (Pixel x coordinate), PY (Pixel y coordinate), WX (World X coordinate), and WY (World Y coordinate).

Ground control point 1

For WX and WY, enter the longitude and latitude, respectively, for the first ground control point.

ground control 1: completed

Repeat the same steps for the second and third ground control points.

All three ground control points are entered

As soon as you enter three points, Geographic Imager will display the residual error values on the table for the accuracy assessment.

GCP Error

A residual error is the computed difference between an observed source coordinate and a calculated source coordinate. It is the measure of the fit between the true locations and the transformed locations of the output control points. A high residual error indicates possible error in either the observed source coordinates or the reference coordinates of the reference point in question.

When the error is particularly large, you may want to remove and add control points to adjust the error. As a general rule, apply several different transformation methods, select/deselect questionable points and select the method and reference points that yield the minimum residual error, assuming that the defined reference points are correct. Residual values are calculated via the associated error values between computed values and entered values through either the affine or various polynomial methods.

Once completed, the Geographic Imager main panel will indicate the georeference information of the image. Don’t forget to save the file once it is complete. Now your image is ready for any Geographic Imager function. You can also bring this image into MAPublisher for Adobe illustrator and align it to other GIS data.

Georeference information displayed on the Geographic Imager Main panel

New Transformation Method for World Maps in Geographic Imager 3.2

When transforming a world image, there may be artifacts created by the Geographic Imager transformation engine. Below are the results of a WGS84 world image transformed into a Stereographic projection.

Geographic Imager 3.1 transformation result

When we zoom into the problematic area, you can see up close how some artifacts affect the image after the transformation was performed.

Geographic Imager 3.0 transformation result 2

To solve this issue, we are introducing a new projection method called Maximum: World Projection in Geographic Imager 3.2.

We are going to use the same world image used with the previous example and transform it into the stereographic projection. Take a close look at the Advanced Options.

Geographic Imager 3.2: Transformation Dialog box

Under the Performance/quality section, select Maximum / World Projections from the Precision drop-down list and click OK.

Geographic Imager 3.2: Maximum / World Projections option

Below is the result of the transformation with the new method available in Geographic Imager 3.2.

Geographic Imager 3.2 transformation result

Let’s take a close look at the same area where the problem happened with the previous version of Geographic Imager. Now the transformed image does not contain any artifacts.

Geographic Imager 3.2: result (zoom in!)

This option is available since Geographic Imager 3.2. The official version of Geographic Imager 3.2 is available now.