3. Field to GIS. 2. Field Update

Transcription

1 GPS Data Update

2 1. Introduction to data maintenance a. What is it? b. Why is it needed? 2. Uses for data update a. Update attribute data b. Update location coordinates Outline Data maintenance is an ongoing task where data in a GIS is refreshed with current field data. Data update is the process of making GIS data current using GPS equipment and skills. You can update feature (location coordinates) and/or attribute information. The feature attribute values might have changed, or the actual position of a feature might have moved. Data update can be done days, months or years after data were originally collected. You can use coordinates of features from an existing GIS database to navigate to those features and collect attribute data.

3 The Data Maintenance Cycle Data update involves taking data from an existing GIS database, updating it in the field, and then getting the field data back into the GIS.

4 1. Select data to update 2. Import into GPS Pathfinder Office 3. Transfer to field computer (GeoXH) 4. Lock GeoXH configuration if necessary Each of these steps will be discussed in more detail Steps 1: GIS to Field - Overview The first step is to select the data you want to update. Will you be updating an entire GIS layer, or will you select out just part of a layer to update? The next step is to import the data into PFO, which converts it to an imp file. The format of an imp file is the same as an ssf file; it is named *.imp so you can distinguish it from regular GPS files. Once you have imported the data, you can transfer it to the GPS receiver. You can lock the receiver configuration to prevent mistakes that might mess up your data.

5 A. Select data to update Which layers? Filter by criteria? Spatial extent Attribute values Have a strategy for getting the data back into the GIS! Step 1: GIS to Field - Details First, you need to choose the shapefile(s) you want to update. You might want to clip out a certain area, or select features with certain attributes. For example, you might want to update all the trees that were planted in When deciding what to do here, make sure you have a well-thought out strategy for getting the data back into the GIS. You need to think about whether your strategy will create duplicate records, and, if so, how will you deal with them to remove the duplicates in the final product. Depending on how you filter your data, there are many scenarios for how this might work. Just make sure you think about it ahead of time, and have a plan. Otherwise, you could end up with confusion and extra work getting your GIS database in shape.

6 Imported features should have a unique identifier ID attribute Street name Barcode number Step 1: GIS to Field, cont. Be sure one of the attributes has a unique identifier so you can find it in the field. You will use the unique ID to confirm that the feature you navigated to in the field is the same as the one on your field computer/receiver. For example, when navigating to lightposts to be updated, you could check the ID tag on the post to see if it matches with the feature you want to update.

7 B. Import into GPS Pathfinder Office File types ESRI shapefiles MapInfo MIF dbase/access (points or positionless features only) Transfer data files from GIS to Pathfinder Office Import utility: *.shp *.imp (ssf file format) Step 1: GIS to Field, cont. Next, you will import your GIS files into Pathfinder Office. You can import shapefiles, MapInfo files, or database files into PFO. You will convert them to *.ssf files which allows you to update coordinates and attribute data. The imported files will have an imp extension, but they are the same format as ssf files. The extension of imp is given so you can differentiate between files that have been imported and files that have not been imported. Note: it is possible to directly import shapefiles into TerraSync on the receiver, but the new location and attribute data cannot be edited or differentially corrected in PFO. So, it is better to import the shapefiles into PFO, which converts them to *.ssf files, which can be edited and differentially corrected.

8 Import setup Type of data to import - Data Dictionary File Only - Features with External Data Dictionary - Features with Data Dictionary Step 1: GIS to Field, cont. During the import, you can choose to import only a data dictionary from a shapefile. In this case, PFO autocreates a data dictionary from the shapefile attribute table; no features are imported. Another option is to match the shapefile with an existing data dictionary. You will normally do this if you are updating data that was originally collected with a specific data dictionary, and you want to use that data dictionary when updating the data in the field. A third option is to have PFO create a data dictionary from the shapefile attribute table AND import the features along with it. In this case, you get an imp file with an embedded data dictionary (not a separate ddf file).

9 Which attributes can be changed? ( Not permitted flag) Coordinate system - Specify the correct coordinate system of your shapefiles! - Positions converted to WGS84 Step 1: GIS to Field, cont. You can prohibit certain attributes to be changed if needed, to protect important data. You must specify the correct coordinate system of the shapefiles you are importing. If you make a mistake here, you will not be able to navigate to your features in the field. PFO converts your data from the existing shapefile coordinate system to Lat/long, WGS 84.

10 C. Transfer to field computer (GeoXH) Check available memory first Delete files if necessary PFO Data Transfer utility Transfer GIS data files (now in IMP/SSF file format) From Pathfinder Office to TerraSync Step 1: GIS to Field, cont. Once you have imported you data, you will use the data transfer utility to transfer the imp file to the receiver. You might want to delete old files to avoid confusion and make room on the receiver for the new data. We rarely run out of disk space on the receiver, so this cleanup is probably most helpful to avoid confusion.

11 D. Lock GeoXH configuration if necessary Insure data meet your specs Protect certain tasks Log between features Delete files Transfer configuration file to TerraSync Step 1: GIS to Field, cont. If needed, you can lock the receiver configuration to make sure the GPS settings are not changed, or to insure that the user cannot turn on (or off) log between features, or delete files that you don t want them to delete. This configuration file can be transferred to TerraSync.

12 A. Check real-time status B. Open the existing data file C. Navigate to previously collected features Verify features (positions and attributes) Update your GIS data Attributes Location coordinates D. Collect new features if desired E. Close data file Step 2: Field Update When you get out to the field, make sure you are receiving real-time corrections so you will be able to navigate to the features to be updated. With WAAS, you should be able to get within 1 meter of a feature; without it, you will only be able to get within 5-10 meters. When you open the imp file, you will be taken to the Data Update screen (this automatically happens whenever you open an existing file). You can select features to navigate to, find them, and then update the attributes or re-map the location coordinates. Remember to verify that you are at the correct feature. You can also collect new features if needed. Once you are finished updating data, remember to close the data file.

13 A. Transfer updated file to PFO Run differential correction Editing B. Export to GIS Status Flags New - brand new feature, not in imported file Updated - imported feature, modified Imported - imported feature, unmodified Re-export data using these flags as filters Create prj file Step 3: Field to GIS When you get back to the office computer, you will use the Data Transfer utility to transfer the updated file to PFO. You can then differentially correct the file, and perform preliminary editing. Once that is completed, you will export the data to your GIS. You can choose which features to export. Decisions here will be made based on your pre-established strategy for integrating the data back into the GIS. Don t forget to specify the correct prj file when you export (this should match the coordinate system of your GIS dataset).

14 C. Re-integrate data into GIS (carefully!) Replace existing layers? Add to existing layers? Merge with existing layers? Step 3: Field to GIS Be very careful when re-integrating the data into the GIS. It is easy to make mistakes here and lose data. Make sure you have a well-thought out strategy and don t be in a hurry.

15 7 Things to Take Away Today 1. Data maintenance involves GIS, PF Office and field components 2. GIS location and attribute data can be updated 3. Have a strategy ahead of time for the update process 4. You must specify the correct coordinate system when importing GIS data 5. Convert to *.ssf files because they can be edited and differentially corrected 6. You can lock configurations to protect your data 7. Be careful when integrating data back into GIS!