GPS Mapping Projects. 5 Steps Required for Success

Transcription

1 GPS Equipment Setup

2 1. Field Reconnaissance 2. Mission Planning 1. Create a project 2. Build a data dictionary 3. Check satellite availability 3. Equipment Setup 4. Data Collection / Data Update 5. Data Processing GPS Mapping Projects 5 Steps Required for Success These steps, if performed properly, will ensure success of your GPS mapping project. Proper planning will help you avoid problems, collect high quality data, and create an organized and complete dataset for your GIS work. This slide show will focus on equipment setup for your project.

3 Equipment Setup 1. Check battery 2. Transfer data dictionary 3. Configure TerraSync settings 4. Check satellite availability 5. Check base station For a successful mapping session, your equipment must be properly prepared. This includes checking to make sure batteries are fully charged, transferring a data dictionary to the receiver, configuring settings in the TerraSync software, checking satellite availability and adjusting survey times if necessary, determining which base station you will use for differential correction, and checking to make sure the base station is operating. A few general notes about the GeoXH will be presented first, then TerraSync settings will be discussed.

4 GeoXH Mapping Components GeoXH Hardware Field computer GPS receiver Receiver Software Windows Mobile OS TerraSync (data collection) Windows Mobile Device Center (file transfer) Office Software Windows Mobile Device Center (file transfer) Pathfinder Office (data processing) Trimble Planning (checking satellite availability) * With Windows XP you must use Microsoft ActiveSync The 3000 series GeoXH is a field computer with a built-in GPS receiver. It uses a Windows-based operating system (Windows Mobile version 6) and has TerraSync software installed for GPS data collection. File transfer between TerraSync and an office computer requires Windows Mobile Device Center (for Windows 7)* and the data transfer utility in PathfinderOffice software. It is important to use a guest relationship when connecting the receiver to the office computer using Windows Mobile Device Center. This appears as Connect without setting up your device. Note: setting up your device creates a synchronization partnership - this will cause problems and is time consuming to undo!

5 Program memory (similar to RAM) 128 MB Used for running programs Cannot use it to save data Storage memory (similar to a hard disk) 1 GB Used for storing programs and data Non-volatile flash memory (not affected by power loss or resetting) GeoXH Memory The GeoXH has two storage areas for programs and data: program memory and storage memory. TerraSync is installed in storage memory. When the GeoXH loses power or is reset, it turns off, and program memory is cleared. Pre-installed documents and program files are not affected by power loss or resetting. However, you can still lose data if you accidentally delete or overwrite it.

6 Screen unresponsive (not blank) Soft reset Use tip of stylus to lightly press the Reset button If soft reset doesn t solve problem Hard reset Hold down power button as you use stylus tip to lightly press the Reset button Resetting If the screen is blank, the handheld has turned off. Press the Power button to turn it on. If the GeoXH locks up and will not respond, you will have to do a soft reset. A soft reset saves data and closes all open applications, then restarts the handheld. All data and settings are retained after a soft reset. If a soft reset does not solve the problem, you will have to perform a hard reset. A hard reset retains settings and data that you have previously saved on the handheld. However, any unsaved data may be lost.

7 Map: view features, background files and GPS breadcrumb trail Data: create files and collect data, manage data and background files TerraSync Sections The TerraSync software has 5 main sections and several subsections for each of the main sections. Navigation: navigate to features using Direction Dial and Close-up screens Status: view satellite info, receiver info and real-time correction source Setup: configure TerraSync

8 Critical Affect the quality and usability of GPS positions Display Affect how the receiver displays information Have no impact on data Two Types of Configuration Settings When configuring the TerraSync software, keep in mind the two types of configuration settings. Critical settings are important for ensuring data quality, and must be checked before each mapping session. Display settings can increase the efficiency of your data collection session. Display settings such as coordinate system and units do not change the data, they only change how the data are displayed on the receiver.

9 GPS settings Masks Max PDOP Min SNR Min Elevation Logging settings Antenna height Logging interval for features (available when a data file is open) Accuracy-based logging Real-time settings Critical Settings Critical settings affect the quality of your GPS data and should be carefully considered. An appropriate configuration can make your data collection session easier and your data more accurate. Keep in mind the following. - It is important to check the configurations each time before you go out in the field. - Ideally, you should use the same configurations throughout your entire project. - Configuration info will become part of your project metadata. Note: you can also use the Configuration Manager utility in PF Office to create a configuration file.

10 Display Settings Coordinate settings Unit settings Note: ALL GPS data are collected in lat/long, WGS 84, HAE they can be displayed in other coordinate systems if the user desires The coordinate system does not change until you export your data Display settings are basically user preferences. They do not change the data, they only change how the data are displayed on the receiver. Remember, regardless of the coordinate system setting you choose on the receiver, your GPS data are collected in latitude/longitude using the WGS84 datum and the height above ellipsoid (HAE) height system. If you prefer, you might choose to display the data in UTM or State Plane coordinates, use feet, rather than meters for displaying distances, or use mean sea level (MSL) for displaying elevation. Changing the coordinate and unit settings does nothing to your data, if only affects how the data are displayed. Coordinate and unit settings are usually chosen for convenience or user preferences.

11 E 496, N 5,057, Zone 12 N, NAD 83 Display Settings That said, if you are navigating, coordinate settings are critical. If someone gives you a set of coordinates that you need to navigate to, you must set the coordinate system on the receiver to match those coordinates. Otherwise, you will be unable to navigate to the target. For example, your friend gives you the UTM coordinates of a favorite fishing hole. You enter in the numbers correctly, but you have your receiver set to display in State Plane coordinates. Once you set your target and start navigating, the receiver will be directing you to a location that is possibly on the other side of the Earth. Also, if you are displaying a background image on your receiver (for example, a color aerial photo) you must set the receiver to the same coordinate system as the aerial photo, otherwise it will not display. The GeoXH receivers are not able to reproject on-the-fly like ArcMap does.

12 Drag slider bar left to decrease GPS precision Drag right to increase GPS precision Recommended settings for postprocessing Max PDOP: 20 Min SNR: 33 Min Elevation: 5 Recommended settings for real-time Max PDOP: 6 Min SNR: 39 Min Elevation: 15 GPS Settings The default GPS settings are at the far left of the Productivity/Precision slider bar. This allows the receiver to collect the maximum amount of data from all satellites in view. When you post-process your data, the software will filter out any bad measurements and give you the best accuracy possible. If you don t plan to post-process your data, you should restrict the settings to force the receiver to only store good quality measurements (middle setting on the slider bar). You can clear the slider check box if you choose to enter specific values for GPS settings. Remember, GPS settings are critical settings.

13 Specify parameters used to calculate accuracy estimates Option to use accuracy-based logging Logging Settings Use this form to configure parameters that TerraSync uses to determine the estimated accuracy of the current GPS position. In this example, TerraSync will calculate horizontal estimated accuracy based on the assumption that you will be postprocessing your data. Clicking the wrench icon allows you to choose these settings. You also have the option to use accuracy-based logging, which only stores features once they meet the accuracy you specify. More detail on this will be provided in the next slide.

14 Can automatically pause logging of point feature or vertex when minimum # of positions is recorded Enter an accurate antenna height and specify type of antenna being used Specify whether or not positional data can be updated Specify whether confirmation is required before you are allowed to close an updated feature Logging Settings The Point/Vertex Auto-pause Count tells the receiver to pause logging of a point feature or vertex once you have recorded a minimum number of positions that you specify. In this example, a point feature or vertex is automatically stored after 5 positions are recorded). An accurate antenna height is critical for high accuracy data collection. Allow Position Update is used when performing Data Update. You can also choose to display a confirmation message when closing an updated feature during Data Update.

15 Select the parameters that TerraSync uses to estimate accuracy of GPS positions Horizontal or vertical In the field or postprocessed If postprocessed, distance to base station Choose whether or not to use accuracy-based logging Accuracy Settings Accuracy settings allow you to select the parameters that TerraSync will use to estimate accuracy of the current GPS position. The value is displayed on the status bar next to the Estimated Accuracy icon. Horizontal or vertical accuracy estimates can be displayed. You can choose to display in-the-field accuracy or expected accuracy after postprocessing. The distance between rover and base is taken into account when TerraSync estimates accuracy after postprocessing (remember, the closer you are to the base station, the higher your accuracy will be). You can set up the receiver to only store features once a specified accuracy level is met. This is based on choices that include whether you plan to postprocess your data or use a real-time correction source in the field. If you plan to postprocess, the distance to your base station will be taken into account.

16 Filename prefix used to determine first character of default filenames Between feature logging used to map a breadcrumb trail based on Time Distance Logging Settings, cont. Please do not change the filename prefix on the MSU GPS Lab receivers, as these are unique receiver identifiers. Having a different filename prefix for each receiver avoids the problem of having duplicate filenames for files collected at the same time with different receivers. Waypoint filename prefix defaults to W. (You can create and use waypoint files if you have coordinates that you want to navigate to). You can choose to map a breadcrumb trail using Between Feature Logging based on time or distance travelled.

17 TerraSync software uses highest priority real-time source available, according to your list of preferences Switches according to availability Real-Time Settings TerraSync always uses the highest priority real-time source available, according to your list of preferences. If the source it is currently using becomes unavailable, TerraSync switches to the next choice. Whenever the TerraSync software acquires a higher priority real-time source, it switches back to this source. The real-time age limit is the maximum age at which a correction message will be used.

18 Coordinate system for display of foreground and background files or for navigating Display setting only, does not convert the coordinates All GPS data are collected in Lat/Lon, WGS84, HAE This does not change until you export your data Coordinate System Settings The Coordinate System settings determine which coordinate system is used for display of GPS data and background files such as aerial photos. If you are navigating using a reference map (such as a topographic map), you must set the coordinate system to match your reference map, or the navigation will not be correct. Changing the coordinate system does not convert the data, it only changes the way data are displayed. All GPS data are collected in the geographic coordinate system (Latitude/Longitude) using the WGS84 datum, with elevation values measured in height above ellipsoid (HAE).

19 Display settings only, does not convert the data Distance Area Velocity Angle Lat/Long Format Offset Format Critical setting when specifying an accurate antenna height Critical setting when navigating North Reference Magnetic Declination Units Settings Unit settings determine the display units for distances, area and angles, and specify how Offsets and North Reference will be displayed. The choices for Offset format are horizontal/vertical or slope/inclination. The choices for North Reference are Magnetic and True North. You may enter a Magnetic Declination or use an Automatic declination calculation. When you are navigating using a reference map, you must set the units to match your map.

20 Battery power? Data dictionary transferred? Receiver settings configured Satellite availability optimal? Base station? Check Equipment Status Before going out to the field, be sure to check these items: Don t leave home without fully charged batteries and backup battery power if necessary. Don t forget to transfer the correct data dictionary to the receiver. Always check your configuration settings before going out to the field. Don t forget to check satellite availability you might be sorry! Be sure to determine ahead of time which base station you will be using for differential correction. How can you check to make sure the base station is operating?

21 Internal antenna: 12-channel L1 code & carrier Vehicle: magnetic vehicle mount Patch antenna (low cost solution, lower accuracy) Hurricane or Zephyr antenna (screw onto mag mount) Canopy: use range pole or backpack to elevate antenna above your head Patch antenna w/ground plane (low cost solution, lower accuracy) Hurricane antenna (best yield & performance) Best accuracy in all modes Zephyr antenna: 12-channel L1 (code & carrier) & L2 carrier 10 cm accuracy with H-star processing Antenna Options for GeoXH If your project requires you to be hands-free, or if you need to elevate the antenna in areas with obstructions or heavy tree canopy, you should consider using an external antenna, rather than the internal receiver antenna. The patch antenna has a magnetic bottom which will attach to any metal surface including a car roof, a metal washer attached to a hat or helmet, or a magnetic pole mount. The Hurricane and Zephyr antennas can attach to a magnetic vehicle roof mount or a range pole. Hurricane & Zephyr antenna Patch antenna

22 Antenna Options for GeoXH A Hurricane or Zephyr antenna can be mounted on a pole and connected to the GeoXH via a cable. The receiver can be placed in a belt pack or backpack when you are moving (and not needing to interact with the receiver). For example, you can start a line feature, set the logging interval, press Log, place the receiver in the pack, and start moving. Once you reach the end of the line feature you can take the receiver out of the pack, press pause, enter any attribute data needed and then close the feature.

23 Antenna Options for GeoXH This photo shows a Hurricane or Zephyr antenna pole mount in a belt pack. This setup makes it a little easier to move around (as opposed to a full-size pole mount).

24 Antenna Options for GeoXH If you need to map offsets, a laser rangefinder can come in handy. This model is larger and heavier than a hand-held rangefinder, but it has better accuracy. However, it is still only accurate to +/- ½ foot, so will introduce some additional error in your mapped features. This photo shows a Hurricane antenna, laser rangefinder, and GeoXH all mounted on an adjustable pole.

25 Antenna Options for GeoXH Advanced class of Fall 2007 using laser rangefinder with survey grade receiver.

26 6 Things to Take Away Today 1. Lack of preparation is a big mistake 2. Make sure you have enough battery power to complete the task 3. Check configurations each time before going out to the field (and use the same configuration throughout the entire project) 4. Remember to check satellite availability 5. Did you remember to transfer your data dictionary? 6. Know the difference between critical and display settings and know the default coordinate system, datum and height system for all GPS data