The Online Positioning User Service (OPUS) provides simplified access to high-accuracy National Spatial Reference System (NSRS) coordinates. Upload a GPS data file collected with a survey-grade receiver and obtain an NSRS position via email.
For Static Data Collection Reference: Collecting Static Data with the Topcon GRS-1
For Downloading TPS Log Files Reference: Downloading Topcon Static Files With TRU
OPUS requires minimal user input and uses software which computes coordinates for NGS' Continuously Operating Reference Station (CORS) network. The resulting positions are accurate and consistent with other National Spatial Reference System users.
Your computed NSRS position is sent privately via email, and, if you choose, can also be shared publicly via the NGS website. To use properly, please familiarize yourself with the information below.
Using OPUS requires just five simple steps:
Enter the email address (e.g., email@example.com) where you want OPUS to send your solution report.
2. DATA FILE
Provide OPUS a GPS observables data file in any format (for automatic conversion to RINEX format by UNAVCO's teqc converter) or convert it to RINEX yourself first. OPUS also recognizes compressed (UNIX or Hatanaka.yyd) or zipped (gzip or pkzip) files, including multiple data files in a single zip archive. For Topcon users the raw TPS file is accepted.
OPUS accepts receiver epoch rates of 1,2,3,5,10,15 or 30 seconds, all of which are decimated to 30 seconds for processing. Note: Though your data file may already contain survey metadata, including antenna type, height, and mark information; these are IGNORED as NGS has found they are inconsistently formatted.
3. ANTENNA TYPE
Select the antenna brand and model you used. This allows OPUS to determine the appropriate antenna calibration model for processing. Take care! Selection of an incorrect or default antenna may result in a height error as large as 10 cm. See Topcon antenna calibration to help find an exact match.
4. ANTENNA HEIGHT
Enter the vertical height in meters of your Antenna Reference Point (ARP) above the mark you are positioning, as shown in the image below. The ARP for your antenna type, usually the center of the base or tripod mount, is illustrated at Topcon antenna calibration. If you enter a 0.0 antenna height, OPUS will return the position of your ARP.
Press OPTIONS to customize the way your solution is performed and/or reported. Your selections will override the optimized OPUS defaults and should therefore only be employed by experienced users.
PROCESSOROPUS currently provides two distinct processing softwares optimized for different data types:
- STATIC (Best Solution): For OPUS static processing, your data file must contain at least 2 hours but not more than 48 hours of data.
- RAPID-STATIC: For OPUS rapid-static processing, your data file must contain at least 15 minutes but not more than 2 hours of data, with all four observation types (L1,L2, P1 (or C1), and P2) present at each epoch used.