On Target HGIS (iPaq) Tutorial
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HGIS (version 5.xx)
The following tutorial is designed to familiarize users of the basic functions of HGIS. All other topics not discussed in the tutorial can be found in the HGIS users manual on the HGIS website www.starpal.com
As you start HGIS, the main screen (Figure 1) will appear after the user distinguishes whether or not GPS is being used. To open an image or a layer of information, go to File...Layer...Open Layer.
Figure 1: Main Screen
Figure 2: Layer Loaded
Under file type, choose "Image: JPG+JGC" as the file type and select "farm1, logan", or your own image. Click open.
For images, another menu will appear where the datum, and lat/long or UTM and zone must be specified. For this image, the UTM is zone 12. A map of UTM zones is available at this site: www.dmap.co.uk/utmworld.htm. Click on OK. The image will appear as shown in Figure 2.
The Tool menu contains Select, Manual Draw, GPS Draw, Zoom In, Zoom Out, Pan, and the Ruler tool. When not using tools, select Tools Off to prevent unwanted editing to the layer.
Select: This tool is used to select certain items such as points, lines, and polygons to calculate lat/long, acreage, to obtain object attributes and to navigate to points.
Manual Draw: When Manual Draw is selected, the following menu will appear:
Depending on the function desired, the tools may be selected to perform the various functions. To manually draw an item such as a polygon (field boundary), select the Polygon Tool and press the mouse button or stylus on the picture to start the polygon. A Manual menu will appear; select Define New Layer. Choose the fieldname, operation and the type of file that you want it saved as. MIF files are used in programs such as Map Info; Shp files are used in Arc View. Click OK.
Choose where you want to save the file and click Save. Then, the Layer Attributes menu will appear. Attributes such as acres, weed type, and soil type can be added to identify objects at points, lines, or polygons. After adding or deleting attributes, click Create. Every additional point, line, or polygon will automatically be assigned an Auto ID number. Type in the desired starting number and click OK. Initially, polygons can be created by drawing or clicking on various locations on the layer to complete and close the polygon. When the polygon is closed, click Off on the Manual menu. If the file is saved as a MIF file, text can be placed on the screen using the text tool.
GPS Draw: The GPS Draw tool is used to create points, lines, and polygons when attached to a GPS unit. The GPS menu is similar to the Manual Draw menu as far as points, lines, and polygons are concerned. GPS can be started and stopped by clicking the Start/Stop GPS function on the GPS menu. If HGIS is receiving a signal from the GPS unit, a black "X" will appear in the center of the screen. Clicking on the appropriate button in the GPS Draw toolbar can create points, lines, and polygons. Points, lines, and polygons are created by the position of the GPS instead of manually drawing on the image. When creating field boundaries, the polygon will automatically close if a full perimeter is not accomplished.
Zoom In: Zoom In is used to zoom in to a desired viewing area on a layer or image. Clicking on the screen or creating a box on the screen will zoom in on the desired viewing area.
Zoom Out: Zoom Out is used to zoom out to a desired viewing area on a layer or image. Tapping on the screen will zoom out to the desired viewing area.
Pan (Drag): Pan allows the image or layer to be moved up or down and left to right according to the users desired viewing window.
Ruler Tool: The Ruler tool is used to measure distances. When the Ruler tool is selected in the Tool menu, a box will appear in the upper left hand corner of the screen. To measure distance, drag the stylus or mouse with the button down from one point to the other. In order to measure exact distances between nodes, check the snap box in the ruler distance box.
Viewing TerraServer Images with HGIS
NOTE: TerraServer (MSRmaps) has been shut down. There is no direct replacement for MSRmaps but the National Map has many similar features and is found here.
A powerful feature of HGIS is the ability to view georeferenced image files. Microsoft TerraServer, located at http://msrmaps.com, allows free download of topographical and aerial imagery. At the TerraServer homepage, you can either click on the map of the United States to navigate to the specific location, or you can search for that location using the search box.
After the map of the specified location is loaded, you can use the tools on the top of the page to change the size of the map and to change between topographical and satellite images. You can click on the map to center and zoom in. In most locations, you can zoom in to one-meter resolution.
After you find the map that you like, you are ready to download. Click on the Download icon in the top bar menu.
On the next page, right click on your image and click Save Picture As. For my picture, I will save it as saltlake.jpg. On the left of the page there is a link to GIS World Coordinates. Right-click on this link and click Save Target As. Name this file the same name as the image, but use the extension .jpw. In my case, I will call it saltlake.jpw. This is the georeference file that tells HGIS where the map is located.
Using Microsoft ActiveSync, load these two files on your PocketPC.
How to Georeference Image Files
Most aerial imagery comes with a georeference file. Normally, you can name this file "imagename.jpw" and it will automatically come up in HGIS when you open the image.
Occasionally, imagery is obtained without any georeferencing – a scanned-in image or digital photo for instance. For images that do not have a georeference file, HGIS provides a simple process for creating a georeference file. You must have a GIS file that is already referenced in order to correct the image. For example, if I had an image of a field, I would make a polygon file of the boundary by walking around the field with a GPS or using a referenced image and tracing a polygon around the edges.
First, open the GIS layer of the boundary (Figure 3).
Figure 3: Boundary of area
Second, open up the image to be georeferenced. A wizard will then start to help you georeference the image (Figure 4).
Figure 4: Dialogue box after image is opened
Third, the image toolbox will pop up and the image is ready to be rectified (Figure 5). Drag a known point (corner) on the image to a location on the polygon (boundary).
Figure 5: Image underneath the boundary file
Fourth, find the known location of the boundary file on the image and drag the image to the right location on the boundary file. Once the first point is correct, tap next and drag the image to another point until the image fits the boundary file (Figure 6).
Figure 6: Adjusted image to boundary file
The image can be adjusted by tapping back, zooming in or out, or moving the image in any direction using the < > keys (Figure 7). Once the image is adjusted in the correct position, tap Done and Yes in the Save Image dialogue box.
Figure 7: Finishing the image geocorrection
Georeferencing Imagery Using a GPS Unit
- Connect the iPaq to the GPS.
- Open the image in HGIS and click on the Advanced button on the wizard to bring up tools.
- With the GPS connected to HGIS, position yourself at a known location that is found on the image. Then drag the image around until you match that spot with the "X" for your position.
- Click Next on the wizard. Position yourself at another known location. The image can then be zoomed and rotated by dragging the stylus. Match the "X" to the second location on the image.
- Click Next on the wizard. You can drag the corners of the image to adjust for error. Click Done and save your finished work.
To complete the exercise portion of this tutorial, the farm 1 image and shape file must be opened. In these exercises, creating soil sampling grids, Greatest Circle calculations, acreage calculations, and georeferencing pictures will be discussed.
Soil Sampling Grids
To create a soil-sampling grid on a field boundary, click on the Select button in the tools menu and click on the perimeter of the boundary. The boundary is selected when small boxes appear in the four corners of the boundary.
Once these boxes appear, click Help...Misc Functions...New Grid Layer. The Create Grid Layer box will appear. Grid type, shape and size of each grid can be selected by choosing from the various drop list boxes. For this exercise we will select square grid cells, each at 2.5 acres.
Once the grid has been set up, points can be manually placed in various locations on the grid using the manual draw tool in the tools menu. To navigate to these points, the user can visually use the black "X" on the screen to walk to the desired point or use the GPS Navigation function in the GPS menu. A box will appear giving the necessary direction of travel and feet left to arrive at the desired location. Located on the GPS Navigation Box is the sample button. Whenever a sample is taken, the sample button can be pressed and a point is manually added to the grid at the sample location.
After a field boundary has been created using GPS, the Greatest Circle function can calculate total acreage covered if a center pivot was placed on the field. Using the Select function in the Tool Menu, click on the perimeter of the field.
After the perimeter has been selected, click on Help...Misc Functions...Greatest Circle. A box will appear in the upper left hand of the screen. Distance of the Extension arm and the End gun in feet or meters can be selected as well as a Variable Extension Arm check box. For this exercise, we will use a 30 ft. end gun without a Variable Extension Arm.
After clicking OK, click Define New Layer and give the layer the appropriate name. Save the file in the appropriate file and click Save. The attributes box will appear and attributes can be added if desired. Click Create.
The boundary will appear in the field and the Boundary Draw Style box will appear. Perimeter and interior line color and thickness can be changed using the appropriate tools. Click OK. The interior boundary of the pivot will appear and another Boundary Draw Style box will appear. Perimeter and interior line color and thickness can be changed using the appropriate tools. Click OK. Another box will appear and actual radius, actual area and coverage with end gun will be given in meters, hectares and acres. Click OK.
The interior circle is coverage of the pivot without the end gun coverage and the exterior circle is the pivot coverage with the end gun. Acres can be looked at again by selecting the circle and selecting Map...Show...Object Info. To change the units of measurement, select File...Options.
Any size or shape of polygon can be manually drawn or drawn using GPS to calculate acres. After the field boundary has been created, use the Select tool in the Tools menu and click on the field boundary. When the perimeter is highlighted, click on Map...Show...Object Info.