Use of SmartRinex for Post Processed Kinematic Surveys

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1 Use of SmartRinex for Post Processed Kinematic Surveys This guide is intended to provide the user with a method of working with a Leica SmartNet licence where real time corrections whether with GPRS, GSM or PDL radio are not available. An example of this might be if the battery on your mobile phone has gone flat, or you are in a rural area with no GPRS or GSM coverage. The PPK (Post Processed Kinematic) method of survey records an uninterrupted string of measurement data, consisting of both moving and static elements. It is required that at least five satellites are tracked at all times during this string of data, and in addition that at least 8 minutes of data is recorded before any survey measurements can successfully be processed. This is known as the Initialisation Period. The user needs to have a current Leica SmartNet licence, and be registered on the HTULeica SmartNet WebsiteUTH. The user will also need to have purchased Leica Geo Office Combined, and have the Rinex Import and GNSS Processing options. The disadvantage of this method is that there is no means of predicting the accuracy which will be achieved after post processing, since real time corrections and coordinate quality messages are not present whilst on site. However, careful monitoring of the DOPs, number of satellites and cycle slips, and ensuring that adequate initialisation time is allowed, should enable the user to continue to collect data where significant downtime might otherwise occur. Configuring the Rover For PPK. Step Instruction Screenshots 1 From the main menu, press 3 Manage, then 5 Configuration sets. Highlight the Smartrover PP config set and press F2 (NEW). (If this config set is not in the list, press SHIFT F5 (DEFLT) to redisplay all the default configuration sets. Please note, this will reset all the defaults, so any changes previously made to DEFAULT config sets will be lost.) Type in a name for the new config set (eg SmartRinex PPK) and press F1 (STORE).

2 2 In the Wizard Mode page, press F6 (LIST) to show the list of pages within the config set. This guide will concentrate on those pages required to work in PPK mode. 3 Highlight Real-Time Mode and press F3 (EDIT). Check that this is set to None. Then press F1 (CONT) to 4 Highlight Antenna and Antenna Hts and press F3 (EDIT). Check that the correct antenna type is selected. Then press F1 (CONT) to return to the Quick Access page. 5 6 Highlight Display Settings and press F3 (EDIT). Highlight Define: Mask 1 and press F3 (DMASK). The settings shown opposite are suggested as a means of best monitoring the quality of your position. If you have your own display mask set up eg for coding, use one of the other display masks. Press F1 (CONT) twice to Highlight Logging of Raw Obs and press F3 (EDIT). Edit the settings to those shown opposite. Static & Moving means that raw data will start to be logged as soon as you start a survey. When in survey mode your little man icon in the top status bar will have a wavy line above his antenna to indicate this:. Press

3 F1 (CONT) to return to the Quick Access page Highlight Point Occupation Settings and press F3 (EDIT). Edit the settings to those shown opposite, then press F3 (PARAM). Change the Number of Obs to 5, and check that the Logging Rate is 1.0s. Press F1 (CONT) twice to return to the Quick Access page. Highlight Quality Control Settings and press F3 (EDIT). This page can be used to stop raw data from recording if the GDOP rises above a set limit. Refer to the TSA Best Practice guidelines (available via the HTULeica SmartNet WebsiteUTH) for more information on acceptable GDOP limits. Press F1 (CONT) twice to Now press F1 (STORE). This configuration set is now ready for use. Surveying Using the PPK Method There are certain guidelines which must be adhered to if data is to be collected successfully using the PPK method. At least 8 minutes of continuous data from at least 5 satellites is recommended in order for LGO to have enough data to calculate static survey positions. Therefore if the data is interrupted at any time (cycle slips, going under trees), the user must ensure that another initialisation period is observed before continuing with measurements. Particular care needs to be taken around obstructions or trees. The configuration we have set up means that the receiver is logging data as soon as the survey page is opened, so other than ensuring that enough satellites are continuously tracked for the required 8 minutes, nothing further needs to be done for the initialisation. When measuring the static survey points, each point must be occupied for a minimum time of double both the logging rate, and the interval rate of the SmartRinex data to be ordered from the HTULeica SmartNet WebsiteUTH. So if the rate is set at 1sec, each point should be occupied for at least 2secs. This is to ensure that at least one common epoch is measured at each point. The settings that we have set are for a 5 second occupation at 1 second logging rate, so with 1 second SmartRinex, there should be at least 3 common epochs recorded.

4 Downloading and Processing With SmartRinex Step Instruction Screenshots 1 Go to the HTULeica SmartNet WebsiteUTH, click on the Subscriber Web Tools icon, then select Smart Rinex Service from the menu at the left hand side. This will take you to an online SmartRinex request form. 2 Fill in the required fields in the online request form. The station information which is requested will produce a Rinex file for a ghost reference station, which your surveyed PPK data will be processed in relation to in LGO. Alternatively, use the Google Map button at the bottom left to position a balloon at the centre of your site. Note: the requested height is ellipsoidal. 3 4 You will receive notification that your data is ready via . You can follow the link to the Results area on the Leica SmartNet website, where the files will be available to download. It is possible to view the status of your request at any time, along with any previous Rinex, SmartRinex and Computation Service requests. Import the Rinex data and your raw survey data into a project in LGO. When you have done so, click on the GPS Proc tab, then right click in the right hand side and select Processing Parameters from the dropdown menu. Check that the Advanced Parameters box is checked in the General tab. Check that the settings match those shown.

5 5 Now go to the Strategy tab. Check that the settings match those shown. Click on OK. 6 7 Now to select the intervals to process. Click on the icon in the toolbar to select all intervals as Rover, then click on the icon, then the long top bar in the right hand pane, which will be the interval for your ghost reference station. Right click in the right hand pane again, and select Process from the dropdown menu. LGO will automatically open the Results tab when processing is completed. Ensure all the results are highlighted (use CTRL+A to select all), right click in the right hand pane and select store. 8 Your data is now processed, and your points will have a measured triplet. Further Hints Each interval should be linked to the next by a thread, which shows that the data has been collected in a continuous stream. Any intervals without this thread indicate a break in the data. By finding the start and end times of any short data streams, the length of the stream can be ascertained and potentially doubtful data identified. To introduce some redundancy and improve confidence in your results, consider downloading SmartRinex data for more than one position around your site. This will enable multiple baselines to be measured to each position.