# Presentation: 271271

## The Global Positioning SystemAdvanced Tools

- <date/time>

- The Global Positioning SystemAdvanced Tools

## Standard Positioning Service (SPS ):
Selective Availability:	0 to 100 meters
Ionosphere:		5.0 to 7.0 meters
Troposphere:		0.5 to 0.7 meters
Satellite clocks:		< 1 to 3.6 meters
Orbital errors:		< 1 meter
Receiver noise:		0.3 to 1.5 meters
Multipath:		undetermined
User error:		Up to a kilometer or more
Errors are cumulative!

- <date/time>

- Sources of GPS Error

**Standard Positioning Service (SPS ):**
**Selective Availability:****	****0 to 100 meters**
**Ionosphere:****	****	****5.0 to 7.0 meters**
**Troposphere:****	****	****0.5 to 0.7 meters**
**Satellite clocks:****	****	****< 1 to 3.6 meters**
**Orbital errors:****	****	****< 1 meter**
**Receiver noise:****	****	****0.3 to 1.5 meters**
**Multipath:****	****	****undetermined**
**User error:****	****	****Up to a kilometer or more**
_**Errors are cumulative!**_

**Notes:**
Let’s look at the “Error Budget”.  If you draw a line through SA then the next two major sources of error that you can rectify are Ionospheric and Tropospheric degradation of the GPS signals.
In times of high solar activity these errors can be relatively significant.
Iono and tropospheric errors can be corrected in two ways:
1) Differential Corrections
2) The use of dual frequency reception 
All other errors cannot be reconciled through these techniques. 
“User errors”, the only left major source of error, can come in the form of improper selection of datums and projections or use of improper field data collections techniques.
Now, let’s look at these techniques.

## Dual Frequency Positioning

**This time difference can be calculated and used to correct for Ionospheric and Tropospheric created errors.**

**Signal propagates through atmosphere ****at different rates due to different ****frequencies.**

**Notes:**
The GPS system, at present, only has two frequencies. Referred to as L1 and L2. One of these frequencies, L2, is a military frequency that cannot be used by civilian grade receivers. 
At the present time, the National Park Service in conjunction with many other federal civilian agencies has an MOA with the DoD for use of the L2 frequency. The federal civilian agencies can access the both L1 and L2 frequencies through the use of a military grade GPS receiver ( Rockwell PLGR 2 ). PLGR 2’s are dual frequency operations.... They are  NOT the same as the PLGR +96’s! PLGR +96’s are single frequency.
This situation is due to drastically change in the next five to ten years. New frequencies are being added to the next generation of satellites so that dual frequency will be available for all civilian users.
As this becomes more available to us, we will no longer have the need to use the military frequency and will migrate away from use of military receivers.
Note: Single frequency C/A Code receivers have about the same accuracy as the military PPS or PLGR+96 now that SA has been set to zero.

## Post-Processed Differential GPS

- <date/time>

**Notes:**
The second and most well known of how to overcome the major remaining GPS errors is with Differential Corrections. 
There are two methods of providing differential corrections for your data.
One is “post-processed”. This means that field data is collected and the differential corrections are done to the positional data when you return to the office.

## Post-Processed Differential GPS

- <date/time>

- Trimble’s Pro XR

- Trimble Geo CE
- XT and XM

- Trimble GPS Pocket

**Notes:**
For post-processed differential operations base station data is for the most part available everywhere in the US, Alaska and Hawaii via internet download.

## Real-Time Differential GPS

- <date/time>

**Notes:**
The other is realtime differential corrections. This method provides you with the corrections to your positions while you are acquiring them.

## NDGPSNationwide Differential Global Positioning Service

- <date/time>

**NDGPS**Nationwide Differential Global Positioning Service

***Advantages:***
-   1 meter, 95% real-time accuracy when the user     is within 100 miles of station
-  Optimized for surface (maritime and terrestrial)    applications with medium frequency,   “ground hugging” signal and is *not* line-of-site    dependent
-  Fully operational in areas of coverage

**Notes:**
Two sources of real-time differential corrections are land and satellite based. The Nationwide Differential Global Positioning Service is a land based system. There are 84 NDGPS sites as of September 2002.

## NDGPSNationwide Differential Global Positioning Service

- <date/time>

**NDGPS**Nationwide Differential Global Positioning Service

***Disadvantages:***
-  Accuracy degrades at a rate of approximately 1    meter per hundred nautical miles
-  More user equipment needed for most receivers
-  Can be susceptible to RF interference
-  Accuracy and usage are distance dependent
-  System is operational but the coverage not completed yet

**Notes:**
Two sources of real-time differential corrections are land and satellite based. The Nationwide Differential Global Positioning Service is a land based system. There are 84 NDGPS sites as of September 2002.

## GPS / NDGPS Beacon System

- Trimble’s “BoB”

- CSI’s MBX3
- Beacon Receiver

**Notes:**
Here are some examples of different types of real-time differential receivers that use the Coast Guard or NDGPS ground based system to acquire their differential correction information. 

## NDGPSNational Differential Global Positioning System

**Notes:**
The Coast Guard Maritime Differential GPS (DGPS) / Nationwide Differential Global Positioning Service (NDGPS) system has coverage for all the the coastal areas, including the Caribbean, Hawaii and coastal Alaska. In addition, most of the internal continental US is covered with the exception areas on the backside of the Rockies and some small areas in the east. These will, hopefully, soon be covered.

## NDGPSNational Differential Global Positioning System

## WAAS Wide Area Augmentation System

**WAAS**** **Wide Area Augmentation System

** ****< 7 meters real-time accuracy**
** ****Accuracy not distance dependent**
** ****No additional receiver needed**
** ****Inexpensive**

***Advantages:***

**Notes:**
WAAS is the Wide Area Augentation System planned by the FAA for accurate navigation of aircraft. This will be a satellite based differential system providing an accuracy of 1-2 meters. WAAS differential corrections will be more and more a part of how we do differential corrections but will not replace NDGPS.

## WAAS Wide Area Augmentation System

**WAAS**** **Wide Area Augmentation System

***Disadvantages:***
-  Does not work well in canopy cover
-  Satellite are geo-stationary over equator
-  Not declared operational yet

**Notes:**
WAAS is the Wide Area Augentation System planned by the FAA for accurate navigation of aircraft. This will be a satellite based differential system providing an accuracy of 1-2 meters. WAAS differential corrections will be more and more a part of how we do differential corrections but will not replace NDGPS.

## WAAS / Beacon / Omnistar / GPS Receiver System

- CSI’s DGPS Max

**Notes:**
WAAS is the Wide Area Augmentation System planned by the FAA for accurate navigation of aircraft. This will be a satellite based differential system providing an accuracy of 1-2 meters.
At present, the system is functional but experimental and only available in scattered areas of the US. It will in the next few years become operational and should provide world wide coverage.

## Why Should You Do Differential Corrections?

- <date/time>

*Why Should You Do* Differential Corrections?

-  Improved Accuracy    ( *still have atmospheric degradation of sv signals* )
-  Positional Integrity    ( *Are you where you say you are?* )
-  Geodetic Tie to NGS Monumentation Network

**Notes:**
The Big Question -
“So why do you still need to worry about differential corrections if SA is zero and I am getting 7 to 10 meters?”
- You will more than likely get improved accuracy by eliminating the Ionospheric and Tropospheric degradation of the signal. While this can be insignificant, it, also, can be significant and, generally speaking, is not a rapidly changing variable.
- Positional Integrity (or confidence). “Are you where you say you are?” With properly applied differential corrections comes a positional confidence that you do not have without it. By “properly applied” I mean both use of base station information that is accurate and precise, as well as, having proper differential techniques applied at the remotely collected data. 
Side Note: Some base stations running today may not have accurately surveyed control positions. Remember any error in the base station will be error in your remote data. “Buyer Beware”. All NGS and Coast Guard controlled base stations are accurately surveyed and use proper base station methodology.
- Lastly, doing differential corrections gives you a geodetic tie to a surveyed network of monumentation. The NGS (National Geodetic Survey) survey monumentation network. This may or may not be a factor for you but it is a good practice when mapping.

## What’s Coming for GPS System?

- <date/time>

- Better, smaller and less expensive receivers
- Closer integration into existing equipment, watches, cell phones, data collection devices, etc.
- Dual Frequency, C/A Code
- FAA satellite based differential service - Wide Area Augmentation System, WAAS
-  Double coverage of NDGPS for CONUS

**Notes:**
Let’s look at what’s on the horizon for GPS and Data Collection.

Better, smaller and less expensive receivers
Closer integration into existing equipment, watches, cell phones, data collection devices, etc.
Dual Frequency, C/A Code
FAA satellite based differential service, the Wide Area Augmentation System, WAAS
Double coverage of NDGPS for CONUS

## Latest GPS Technology

- Trimble Geo CE
- XT and XM

- CSI DGPS Max and MiniMax

**Notes:**
Here are some examples of the latest technologies on the market today.

Casio’s GPS watch: around $600, eight channel
Garmin’s GPS V and eTrex, combination GPS and WAAS receiver, around $300 - $450, 12 channel, moving map display. Etrex Vista has digital compass onboard.
CSI DGPS Max and MiniMax are two very nice real-time differential GPS combination receivers. They can provide 1 – 2 meter real-time accuracy. Costs are $1500 - $3000.
Trimble Navigation’s new GPS Pocket, $500, 12 channel and it relies on a data collection device for operation.
Trimble’s Windows CE GPS receivers, the XT and XM. XT is considered a sub-meter unit and the XM is 2 –3 meter. Costs for full systems are between $5000 - $6500. 

## Latest Communication Technology

- Garmin Rino
- FRS / GRSM
- Radio and GPS
- Reciever

**Notes:**
Here are some examples of the latest communication technologies on the market today.
The Garmin NavTalk, this happens to be one example of how GPS and cell phone technologies are merging.
The Garmin Rino’s. Integrated FRS/GRSM Radios with GPS and real-time mapping

## Latest Communication Technology

- Racal Project 25 Voice / Data Radio

- CSI GT300
- GPS Enabled Digital
- Cell Telephone

**Notes:**
Racal (Thales) Project 25 Digital Narrowband Radio with data transmission capabilities.
CSI GPS Enabled Digital / Analog Cell Phone. This cell phone has full GPS capabilities unlike most other “GPS enabled” cell technologies were the phone simply collects only the pseudoranges and does not provide full GPS receiver functionality.

## Latest Mapping Technology

**Notes:**
ESRI’s ArcPAD: A software that will be very important to us and how we collect field data.
With a Pocket PC, ArcPAD software and a GPS receiver you can take a large volume of information (1 to 5 gigs worth) out in the field for reference or editing. Collect your data using forms and store the data in native shape files or geo-databases. ArcPAD can use Mr. SID compressed image files to display aerial imagery, satellite photos or DOQQ’s. In addition, you can utilize all of our existing database templates, shape files, coverages and geo-databases through ArcView and ArcInfo natively in ArcPAD. Copies of software are available to DOI off the enterprise licensing agreement.

Trimble’s TerraSync: This product from Trimble is similar to ArcPAD but has a little less functionality. One plus for TerraSync is that it can use existing Trimble data dictionaries. This product will become Trimble’s standard data collection software and the other software (Aspen, etc.) will no longer be support after a while (no timeframe). Cost for TerraSync is approximately $1500.

## Handheld Mapping

- In-the-fielddata collectionand informationdisplay.

- Combine datasets

- Display valuabledata sources

- Query attributeinformation

## Data Collection Softwares

- Trimble TerraSync
- ESRI ArcPad
- Fieldworker
- TDS Solo CE
- Various PalmPilot Softwares

**Notes:**
ArcPAD is among the many softwares that are out or coming out on the market for handheld data collection either on the Pocket PC (Win CE) or the Palm Pilot.

## Minimum Suggested Handheld Requirements (August ‘03)

- <date/time>

-  Min. 206 Strong Arm chipset
-  32 Mbs of RAM
-  PC Card (or compact flash)    expansion capability
-  Daylight viewable screen!
-  Ruggedized (if possible)

## Panasonic Toughbook 01

*Examples:*

** **Panasonic Toughbook 01    (32 Mbs of RAM)
-  Serial AutoSync cable
-  1 gig IBM Microdrive and / or    512 mb Secure Data card
-  Extra removable battery
-    with charger

**Approximate cost: $2000.00**

## Latest GPS Imaging Technology

- Trimble’s
- Media Mapper

**Notes:**
Digital Imaging with GPS and Attribute Stamping or Watermarking:
This is a digital imaging system using a combination a digital camera and a GPS system.
1) GPS Tag: A script is runs on a Kodak DC290 camera that queries the DGPS system for a position, fix type, datum and horizontal accuracy. It combines this information with user defined information from a simple data dictionary or manually entered attribute and a date/time stamp  and places a watermark on the photo and in the header information of the image.
This information is, also, stored in a comma delimited text file on the camera for download and with an ArcView extension the header information in the file allows the user to automatically create a point shape file with hotlinked photos.
All attribute information is in this text log file (and header info) and gets carried over to the ArcView shape file. Kodak DC 290 cameras are no longer available. Costs are around $40 for the script.
2) GPS Photo Link: This software works with any Garmin GPS receiver and just about any digital camera. No wires. A track is collected on the GPS unit and the photos are matched up in the post-processing software with the location they were taken by matching up the time tags on the photos and the track log. Creates a point shape file with all of your attribute information and a point shape file of your track. Cost is $249.
3) Trimble’s Media Mapper: This software does is about the same as the GPS Photo Link but works only with Trimble GPS equipment. Creates a shape file through Pathfinder Office. Cost is $900.

## Digital Camera/GPS Imaging Systems

-  Latitude and Longitude
-  Datum
-  Elevation
-  FMSS Facilities information
-  Archeological descriptions
-  Viewing direction
-  I&M database unique identifiers
-  Basically, anything that you want    to watermark on photo.

**Notes:**
This is only a few of the many attributes that can be added to your photos and output to your shape file.

## Digital Camera/GPS Imaging Systems

**Notes:**
Example watermarked photo.