III. GPS SURVEY DATA

TABLE OF CONTENTS:

A. Forms

B. Download, Reformatting, and Shipping Instructions

C. Processing
 

See the NGS Links Page

Forms commonly used during a GPS project include the following, described below:

1. Station Description / Recovery Form
2. Station Datasheet
3. Visibility Obstruction Diagram
4. GPS Observation Log
5. Pencil Rubbing Form
6. Volunteer Sign-up Form
7. Meteorology Equipment Comparison Form
SEE ALSO: ASP forms

A-1. Station Description / Recovery Form:	Blank Form	[top]	[home]
The Station Description / Recovery Form is used during field reconnaissance to provide new or updated descriptions for survey monuments. The descriptions on this form shall be entered into WDDPROC software for bluebooking, checked during field observations, and submitted with the GPS data. Descriptions for existing stations can now be submitted on-line.

The datasheet descriptions are checked during field observations, submitted with the GPS data, and entered into WDDPROC software for bluebooking.

A-3. Visibility Obstruction Diagram:	Blank Form Airport Ver. en español	[top]	[home]
The Visibility Obstruction Diagram is used to sketch any trees, buildings, mountains, wires, or other obstructions which may interfere with the GPS line-of-sight satellite signals.  These diagrams are useful during processing to explain signal losses, multipath, or radio-interference. To fill out or check this form, use a magnetic compass to measure bearings and an inclinometer to measure vertical angles to obstructions.  Sketch the surrounding obstructions as seen from the antenna viewpoint.  The diagram depicts a "fish-eye" or "bubble view" of the sky over the antenna.  The edges of the circle are the horizon, and the center of the circle is zenith. This form is filled out during field reconnaissance, checked during field observations, and submitted with the GPS data.

A-4. GPS Observation Log:	Blank Form en español	[top]	[home]
The GPS Observation Log is used to record all equipment, activities, and other metadata associated with a GPS observing session. Please be very careful and thorough when filling out this form.  GPS receivers and antennas must be uniquely identified by manufacturer and model names, and part numbers, and COMPLETE serial numbers.  The antenna setup and height measurements must be explicitly described, using sketches and photographs if possible.  Any non-standard conditions must be noted and explained. To ensure that all entries are correct, have another person check all data on the log and sign the bottom of the form as "Checked by" with their full name. This form is filled out during field observations and submitted with the GPS data.

A-5. Pencil Rubbing Form:	Blank Form Airport Version	[top]	[home]
The Pencil Rubbing Form is used to obtain an impression of the mark stamping for positive identification of the station occupied during a GPS observing session. To make a rubbing of a station disk, the mark should be as clean and dry as possible.  Place the blank form (or other blank slip of paper) over the mark and rub over the entire disk with a pencil (a wide lead, e.g., a carpenter's pencil works best).  If it is impossible to make a rubbing of the mark, or if the rubbing appears indistinct, a sketch and/or photograph can be substituted.  For NGS rod marks, rub only the designation and date stamping from the rim of the aluminum logo cap. This form is filled out during field observations and submitted with the GPS data.

Please submit this form to the NGS Project Coordinator if you are interested in co-observing during an NGS survey.

DATA DOWNLOAD

Using your manufacturer's software, transfer the data from the GPS receiver to your computer two separate times.  Place one copy of the data in a working directory and the second copy in a backup directory.  Compare the files to ensure that uncorrupted data were successfully downloaded to your computer.

Convert the raw GPS data to RINEX2 format with your manufacturer's software.  The software should require you to enter the raw data filename, the output filenames, your name, the observer's name and agency, and the antenna type used.

The NGS-standard data filenames are as follows:
 

Raw GPS input files:	aaaaddds.xxx		Where: aaaa = alphanumeric 4-character station identifier, ddd = day of year, s = session, yy = year of observations, and xxx is the receiver-dependent file extension (e.g., .DAT, .EPH, .ION, .MES, etc.)
RINEX2 Navigation File:	aaaaddds.yyn
RINEX2 Observation File:	aaaaddds.yyo

For example, RINEX2 filenames from station BALD 2 on session A of 12/31/98 are BALD365A.98o and BALD365A.98n

Copy the data files onto CD-ROM or diskettes and label with the following information:

After the completion of three observation sessions, ship the data and original forms to the Project Coordinator.  Use a large First-Class or express envelope, and pad the data with cardboard or several pages of paper for protection.  Include the following forms:

from EACH STATION:

from EACH OBSERVATION SESSION at a station:

The following data should be kept as a backup for at least 5 years:

For data processing guidelines, refer to the NGS Project instructions.

See also Submitting Processed Data to NGS.