Archive for the ‘Tab Tips’ Category

Tab Tip

November 10, 2008

Using a URL Field to Provide Direct Access to GIS Datasets from within XMap

Before jumping headlong into a series of step-by-step instructions that will ultimately achieve the outcome stated in the heading of this article, it would be wise to consider the end product as a means to provide a semblance context for the required steps.

The XMap OpenSpace layer that is available for download here contains a grid covering a portion of Southern Maine, the hinterland of DeLorme’s corporate headquarters. If you import the layer into XMap and zoom to one of the grid tiles, you will notice each tile is labeled “Download” and that this text is an active URL or link. The URL triggers the download of high-resolution orthoimagery for the selected tile in MrSID format. Click one of the links and you will be offered the option to save the corresponding Zipped MrSID file on your local hard drive. Unzip the file and, using the Map Data tab in XMap, add the image to your current project. This is an example of the use of the URL field within XMap for accessing remote data for a selected geographic area.

url_1

url_2

Now that we more clearly understand the goal, we can discuss the steps that were required to create this layer.

Step One – Research the Availability of the Data

In order for this project to be successful, the targeted data must be available for direct download. In the example previously mentioned, the imagery is archived on the Maine GeoLibrary Data Catalog site, where the Find function allows the visitor to search for imagery by 1:24,000 tiles. The result of a search is a long list of MrSID files, each of which can be individually downloaded. Although each of the URLs that are used to download the MrSID files is obviously unique, they follow a standard format:

http://megis.maine.gov/data/ortho_hf/[tile_ID].zip

Step Two - Find a Suitable Frame of Reference

As a means to help identify the specific tile ID for an area, the Maine GeoLibrary provides an index grid in shapefile format. Importing this file into XMap shows the coverage of each tile overlaid on the base map, and the attribute set for this layer includes the unique ID for tile. With this data, I was able to create a new attribute field within the index layer by combining the standard format of the URL identified in step one with each tile’s unique ID.

Step Three – Use a Formula to Create the New URL Field

The process of creating the new field in XMap involved the following steps:

  1. First I clicked the Attributes button and selected Design View 
  2. Then I clicked Options and chose Add Field
  3. After naming the field, I selected URL as the Data Type and changed the String Size from 32 to 100 to accommodate the large number of characters in the URL
  4. In the formula window, I typed the following:
    “http://megis.maine.gov/data/ortho_1f/” & [PHOTO] & “.zip”
    In this case PHOTO was the name of the existing attribute field that contained the imagery tile ID. The following is an example of what the new field looked like in the Datasheet View:
    http://megis.maine.gov/data/ortho_hf/ortho_hf395_4890.zip
  5. Finally I created another new field, this time using the String Data Type and in the formula window, I simply typed “Download”. I used the label function in the Tools menu of the Workspace to assign this new field as a label so that the word Download appeared at the center of each grid and offered access to the previously created URL

Step Four – Click the Download Label on the Map

This index grid now provides the means to download imagery for a selected geographic area.

Anyone using either the Editor or Enterprise versions of XMap can use this procedure to initiate direct access to any data that is archived online or at a remote location, and for which a geometric frame of reference is available.

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GIS Database Synchronization

September 25, 2008

Before we begin to look at the process of synchronizing a GIS database, it should be noted that this level of XMap technology is not going to be appropriate for all XMap users. There are several prerequisites that should be considered before continuing. Therefore, let’s start by asking a few questions:

1. Do you maintain or do you plan to maintain a database of GIS data?

2. Do you have a field-based workforce or technicians at a remote location who routinely need access to this data?

3. Do you periodically update your data and, if so, is it important that your field workers are provided with these updates?

4. Would you benefit from an automated process whereby notes and observations collected by your field workers are automatically sent to you as redline layers?

If you answered “No” to any of the questions then it is unlikely that you will have a need for XMap’s synchronization tools. If you answered “Yes”, then read on to learn how the data synchronization process within XMap GIS Enterprise will benefit your business.

The application of GIS technology to manage   workflow, physical infrastructure, and business systems is a standard practice in today’s business world. A challenge for the enterprise GIS is maximizing the return on investment in GIS through efficient data sharing. XMap 6 has been designed to effectively meet this challenge. Automated database synchronization ensures that your mobile field force is provided with up-to-date GIS data while simultaneously communicating field collected observations or GIS layer updates to the central GIS database. XMap synchronization is initiated by the field worker using a simple button click in the Professional version of XMap and requires no knowledge of GIS data management or data importing. Best of all, XMap 6 is designed to minimize the set-up and maintenance burden on your IT department.

All XMap 6 GIS editions include a locally installed version of SQL Server. With XMap 6 GIS Enterprise,

XMap’s most advanced product version, GIS and IT administrators can set up and manage the deployment of GIS databases in compliance with typical IT protocols, providing efficient data flow to your mobile work force.

The database synchronization set-up process involves a few simple steps:

1. Using Database Manager which is installed with XMap GIS Enterprise, the GIS manager or IT administrator creates a list of users who will have access to the database in which the required layers are stored. Because XMap 6 supports Windows Groups, this procedure can be performed for a large workforce in matter of minutes.

2. The specific layers required by each user or group are tagged or checked.

3. A Subscription file is then created and distributed to each worker for whom access to the database has been established.

4. The field worker double-clicks this file to initiate the synchronization process. This procedure needs to be performed only once.

Typically the recipient of the synchronized data will be using XMap Professional. This field-optimized GIS viewer does not offer tools for editing, so no changes can be made to either the geometry or attributes of a synchronized GIS layer. However XMap Professional does provide the means to perform such tasks as running queries, switching classifications, and selecting objects to reveal the relevant attribute data. Even more important, the synchronized data is copied into a database in the local instance of SQL server providing access to the data without the need for a continuous network connection.

After double-clicking the subscription file as noted above, three new buttons will be displayed in the toolbar in XMap Professional:

• The Synchronize button establishes a connection to the administrator’s database and initiates the transfer of data that has been updated or added since the last synchronization.

• The Redline button opens a pallet of annotation tools that can be used by the field worker to draw lines, polygons, text, and other objects on the map. This annotation layer is transferred to the data administrator when the Synchronize button is next clicked.

• The Add Synchronized Layers button provides a simple way to restore the relevant layers to the GIS Workspace in the event that they were inadvertently removed or if the previous XMap session was terminated without the current project being saved.

One of the most challenging aspects of GIS data administration is providing remote access to updated data. XMap GIS Enterprise has been designed to effectively address this issue with its efficient data distribution capability. With a single click of the Synchronize button, field workers can simultaneously download updated GIS layers while uploading field-collected data in a redline layer.

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Tab Tip – Adding New Attribute Fields to an OpenSpace GIS Layer

May 21, 2008

The Field Creation dialog box is among the most powerful components of the GIS tab in XMap. Admittedly, it is quite difficult to find this tool, but if you click the Design View button in the Attributes tab, you’ll see an Options menu that contains several field management tools including Add Field… Sooner or later, most XMap GIS Enterprise or Editor users will encounter a situation that requires that they visit this area of the software.

The basic function of the Field Creation dialog box is to generate a new field or column of attributes for an OpenSpace GIS layer. For instance, if you import a shapefile containing local property polygons, you may need to add a field that allows you to include information on the value of each property, or if you download waypoints from the Earthmate GPS PN-20 and import them into the GIS tab, you will likely need to use the Field Creation function to assign the appropriate data to each collected location.

 

There are two approaches to creating a new attribute field: you can either create an empty field that allows you to manually type the required information for each object, or you can build a formula that creates data from your existing data fields. An example of the latter would be if you want to convert the values in the area field for a polygon layer from square kilometers to acres.

 In either case, the initial steps for creating a new field are the same:

  • Open the Field Creation dialog box in the attribute Options menu as noted above.
  • In the Field Name area, type a name for your new field.
  • Select a Data Type from the drop-down list.  The most common type selections from this list are String, Integer, and Float (a numeric field-type that allows decimals). It is important that the appropriate consideration is given to this selection as a new data value cannot be typed into an incompatible field. For instance, you cannot enter alphabetic characters into an integer field. Also note that if you need to create a range classification based on the new field, the field-type must be one of the numeric options. For more information on the other data-type options, refer to the help documentation within XMap.
  • If appropriate, select the String Size, which determines how many characters the new field will accommodate.
  • If you need to create an empty field, simply click the OK button and return to the Datasheet View to enter the necessary data. 

The additional components of the Field Creation dialog box control the development of a formula that can be applied to one or more of your existing fields to create new data. To simplify the process, a selection of preformatted functions is provided in the window on the right side of the dialog box. As each function is highlighted, a brief explanation of the resulting formula is displayed at the bottom of the window. To build a formula based on one of these functions, double-click the function name to automatically add it to the Formula window.

 

The window on the left side lists all of the current attribute fields for the selected OpenSpace layer. After highlighting the appropriate section of a formula, double-clicking the required field will automatically add it to the formula.

 

For example, if you choose the AVG(field) formula to generate a new field containing the average property values, highlight the “field” statement in the formula and double-click  the existing property values field to add it to the formula. The new formula will read like this: AVG([Property Value]).

 The Formula window can also be used to manually create a formula. For example, to create a new field that converts the existing Area value in square kilometers to acres, type the following into the formula window: [Area*247.1054].

 For new fields that have been created using a formula, modifying, deleting, or updating the original fields that were used in the formula will alter the values or text that appear in the new field.

 For more information on this or any other XMap function, refer to the Help Topics or click the User Guide link in the software’s Help menu.

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Tab Tip – Customizing the appearance of points in a GIS layer

April 14, 2008

When symbolizing points in a GIS layer your options are virtually limitless. XMap includes dozens of preformatted symbols and it provides the means for you to create your own symbology. Choose from the following alternatives:

 Stock Symbols

The default appearance for all point objects imported to, or created in, the GIS tab is a green circle with a diameter of 6 pixels. This is an example of a Stock symbol in the Symbolize Layer dialog box. Other Stock symbols include a square, a star, and a triangle. These simple shapes are often the most effective way to represent points in a GIS layer as they are easily distinguishable and they produce a relatively tidy map. Another advantage of using stock symbols is that their size and color can be customized so a single shape can be used to represent several groups or classes of related features that can be differentiated by variations in size or color.

 DeLorme Symbol Sets

When XMap is installed, a folder called Symbols is created on your local hard drive. This folder contains several symbol sets that can be assigned to objects in either the Draw or GIS tabs. Options include pushpins, flags, dots, and an extensive and stylish set of symbols that were created for use with DeLorme’s handheld PN-20 GPS receiver. The Set dropdown list in the Symbolize Layer dialog box provides the means to select a symbol set and to choose the individual symbol for the objects in your layer. Note that symbols of this type cannot be resized and their color cannot be customized.

 Custom Symbol Sets

If you have used the draw tools to add points to the map, you are probably familiar with XSym, the simple graphic tool for creating and editing symbols. XSym can be used to open an existing symbol set for editing or for creating a new symbol set. In either case, symbols can be created using the included drawing tools and color palette or by importing a bitmap image, such as a company logo. Bear in mind that the final size of the symbols is 24 pixels square so a complex image file, such as one with a wide variety of colors, will likely not work well as a symbol. After a symbol set is saved using XSym, it can be added to the list of available symbol sets in the GIS tab. In the Symbolize Layer dialog box, click the Add button and browse to the Symbols folder in your DeLorme Docs folder to select the new symbol set (*.dim). Now the new symbols can be selected in the same way as the DeLorme symbols as noted above.

 Bitmap Images

When using the Add button to locate a newly created symbol set, as outlined in the previous paragraph, you may notice that there is an alternative to the .dim format in the browse window. The Files of Type dropdown list also includes bitmap files, which means that an individual image can be added to the symbol set list. This approach allows any bitmap, regardless of its native dimensions, to be attributed to a point object on the map and, therefore, is a viable alternative to XSym for assigning a complex image file to a point on the map. Because there is no size constraint or scaling of the original image, care must be taken when choosing a bitmap for this application. It is quite likely that a large image assigned to each point on the map will result in an untidy cluster of overlapping images.

For more information on symbolization or any other XMap feature or function, check the Help Topics or PDF User Guide that were installed with the software and are accessible from the Help menu on the toolbar in XMap.

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Understanding the Differences between the Draw and GIS Tabs in XMap

March 10, 2008

Long time users of DeLorme software will be familiar with the functionally of the Draw tab. Since the earliest versions of Street Atlas USA, draw tools have allowed users to annotate to the map and to create their own map features. Today the Draw tab is a central component in all DeLorme software titles, both consumer and professional.

forest_stands.jpgFor users of XMap GIS Editor or Enterprise, the importance of the Draw tab has been somewhat diminished with the development of the GIS functionality. While both tools allow points, lines, and polygons to be added to the map, the GIS tab includes the ability to add attributes to these objects. This allows you to develop and manage an extensive database of information, which is tagged to the appropriate location.

As an example, let’s compare the use of the Draw and GIS tools to create polygons for delineating forest stands. In either case, polygons can be easily drawn, the color of the objects can be adjusted as needed, and the geometric characteristics can be edited. Both functions allow coordinate geometry input to create map objects with a high level of precision, and both can be overlaid on any base map or imagery layer. On the surface, therefore, it is impossible to distinguish a polygon created in the Draw tab from one created in the GIS tab.

Taking this hypothetical project a step further, it is likely that the process of mapping the forest stands also involves collecting relevant information about the areas in question and perhaps cataloging such data as the types of species present, the date of the survey, and much more. Unfortunately the Draw tab does not offer the option of adding such attribution to the objects on the map. When using the GIS tab, however, a limitless array of attribute fields can be appended to each map feature and the data they contain can be used to reveal spatial patterns in the distribution of data through a classification process. This function of the GIS tab thematically adjusts the visible characteristics of the objects on the map to reflect the variations in the selected attribution. Furthermore, the Query feature of the GIS tab can be used to quickly locate an object or group of objects based on its attribution or based on its spatial relationship to other map objects. Finally, the GIS tab can used to import and overlay data from third party sources, such as shapefiles or CAD files, which can help create a more complete picture of the area being studied.

With the availability of powerful data mapping tools in the GIS tab, what role does the Draw tab play for XMap users?

  • Even in advanced GIS applications, it is often useful to add a simple text label or a MapNote, which is easily done using the Draw tab.
  • When exchanging data with a GPS receiver, such as the Earthmate GPS PN-20, the Draw tab is used to manage downloaded waypoint and track layers before they are converted into GIS layers, and to create waypoints and tracks to be sent to the PN-20.
  • When employing the data synchronization functionality between XMap GIS Enterprise and XMap Professional, the redlining functionality uses the draw tools to communicate field-collected notes and other annotation with the data administrator.
  • The Draw tab can be used to create routable roads and trails not present in DeLorme’s base maps. 

For these reasons, the Draw tab is still an important feature in the XMap product suite; however, for creating points, lines, or polygons on the map, it is the GIS functionality that provides the more powerful set of data management tools.

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