How to create and use a GIS database of land trust holdings
The core of any GIS for land trusts is a database of the lands held as fee or easement ownerships.
GIS data of land trust holdings are digital polygons (shape files, coverages, etc.) created from accurate base maps and supplemented with attributes about each holding (owner name, status, data acquired, etc.). Creating this database involves first defining where your properties are -- all land trusts should strive to have the most accurate boundaries possible, as much future work will be built on those delineations. You can then add data about each of these properties to your GIS data. LEARN MORE about how GIS data works...
Follow these guidelines when creating a GIS database of your holdings:
- Data Structure - Develop a single structure for the kinds of information you are gathering about your holdings, and make all holdings part of this structure. Instead of creating separate GIS data files for each of your holdings, have all polygons in one GIS file, with common attributes or fields (attributes are like columns in a spreadsheet - for each holding, they include details about that property). If you create separate polygon file for a new holding, be sure to also import it into your database.
- Holding Data Fields - The main fields (or attributes) for holdings are usually: Tax parcel ID number, parcel name, property owner name, address, acquisition date and cost, acreage, status (planned, acquired, transferred, etc.) and notes. Each land trust may have different approaches, but the key is to be consistent in the data you place in each field (same name, spelling, etc.), and to be thorough in completing this information for each property.
- Base Map for Property Data - When collecting information on property boundaries, use the best base map available. USGS 1:24,000 scale "quads" often work well in rural areas, road maps can be used in urban places. If you have access to existing governmental GIS files of property owners in your area, you should use these by copying them into your database or by accurately drawing the same boundaries. Aerial photographs can be very useful in setting accurate boundaries. LEARN MORE about aerial photographs...
- Updates - Maintain your data files carefully, updating them regularly and making good notes as to issues or questions about any boundaries.
- Label Fields - To help in using boundary files to make maps, add a field with a short property name, suitable for a map label, along with one for the more complete name. Short names help when you don't want too much detail on a map.
- Keep Careful Records - Even if you are not using GIS, keep a careful record of your holdings, both on maps and in spreadsheets or databases. Be sure each holding has a unique ID field, to allow for easier transition to GIS in the future. LEARN MORE about land trust mapping without using GIS...