How to Geocode Address-Based Tree Inventory Data

TreePeople's OpenTreeMap.

Mapping your trees is the first step to making more informed urban forestry management decisions. Displayed here is a map of trees across Los Angeles County.

Tree inventory data helps municipalities create urban forest management plans, allocate funding and proactively manage trees to ensure their long-term health. Most tree inventory and mapping software platforms require data to be geocoded, yet many municipalities and nonprofit organizations only track the postal addresses of their trees.

In this post, we will outline how you can geocode your address-based tree data without an expensive geographic information system (GIS) or technical expertise. Geocoding refers to the process of assigning longitude and latitude information to addresses so they can be placed as points on a map.

Why geocode your address-based tree data?

Having address data on your trees is important in order to find the general tree location. We plug addresses, not coordinates, into our GPS in order to find a place. However, geocoded data is important for identifying trees once you’re at a specific location. In both urban and rural settings it is common to find multiple trees of the same species at one address, which can make it difficult to locate a specific tree without additional identifying information.

Not only do maps make it easier to locate a tree in the field, they also help us identify actionable insights and make more informed management decisions. Unlike a spreadsheet of tree data, a map of your trees can help you track the spread of pests and disease, visualize how mature trees are dispersed across your city and identify which areas have the highest tree mortality rates. Additionally, the more people involved in maintaining street trees, the more helpful maps are in coordinating volunteers and municipal employees, and updating key information.

After you go through the process of geocoding your address data, all trees listed at the same address will have identical longitude and latitude. You will need to update this data either in the field or using satellite data as a reference to reflect the exact location of a tree at a particular address.

How does geocoding work?

Most simply, geocoding is performed using a reference layer. The process involves matching the to-be-geocoded addresses from your spreadsheet to the street names and address ranges in a street network file. The system matches the street name in your spreadsheet to a reference table and map. Once the street name is matched, all address ranges for this street are examined to identify the specific segment of a street where the address is found. Since the geocoder knows the coordinates of the endpoints of each street as well as the range of street numbers for a given segment, the software can estimate the address coordinates. Most geocoding services place trees at the front and center of the parcel with the associated address. However, some more advanced services allow you to choose how far off the center point of the adjacent road you want to place a given point.

Once you have geocoded tree data you can upload your data to mapping platforms like Carto, QGIS or OpenTreeMap. Carto and QGIS are not industry-specific; however, OpenTreeMap was designed specifically for mapping urban trees and green infrastructure.

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Texas A&M offers free geocoding services for up to 2,500 addresses.

Using Texas A&M’s Geocoding Service

We’ll walk through the steps for using Texas A&M’s geocoder, which allows you to geocode 2,500 records for free. There are numerous other services available, however, many require technical expertise and/or software licenses. Texas A&M’s geocoder allows you to upload a database (access file) or text file (csv, tsv) of address data to their website and generate latitude and longitude values. The system can geocode thousands of records in minutes.

Geocoding Instructions

  1. Create an free account with Texas A&M GeoServices.
  2. Navigate to the Batch Geocoding page of their website. Click “Start – Step 1>>.”
  3. Click “Add New Database.”
  4. Click “Upload New Database.”
  5. Choose the file from your computer and designate the type and click Upload. For this example, we used a comma separated values (.csv) file. Make sure to follow the file naming notes listed on their website and include column names in the first row of your spreadsheet or database.
  6. Once you validate that the geocoder can open and read your file, choose the columns from your file that want to process. The required fields (“Address”, “City”, “State”, and “Zip”) must be present in your database or file even if these fields are blank. The system will not process records without these fields present.
  7. Use the dropdown lists to identify the fields in your table that correspond to the input fields the geocoder expects to see. Make sure to only select each of your fields in a maximum of one dropdown.
  8. Choose your processing options and Click “Start Process.” Rather than wait to view your results you can opt-in to receiving status notifications via email. You will receive an email with a link to download your geocoded data once the process is complete.
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A spreadsheet highlighting the four columns created after the geocoding process was complete for Rehoboth Beach, Delaware.

In the spreadsheet above, we have highlighted the four columns added after the geocoding was completed. You can reference Texas A&M’s website for additional technical details on how the longitude and latitude results were generated and explanation of the values for the “MatchType” column. 

We took the newly geocoded data and uploaded it to the three aforementioned mapping platforms: Carto, QGIS and OpenTreeMap.

We mapped Rehoboth's recently geocoding trees using QGIS, a free and open-source desktop geographic information system (GIS) application.

First we mapped Rehoboth Beach’s trees using QGIS, a free and open-source desktop geographic information system (GIS) application.

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Second, we mapped Rehoboth Beach’s trees in Carto, a cloud computing platform that provides GIS and web mapping tools for display in a web browser.

Rehoboth Beach trees plotted on OpenTreeMap.

Lastly, we plotted Rehoboth’s trees in OpenTreeMap, a cloud-based software for mapping and managing trees and green infrastructure.

The less accurate information you have on tree location, the higher the chance the wrong maintenance task is performed on the wrong tree. At best, this results in the misallocation of finite resources and at worst potentially removing an otherwise healthy tree. With geocoded inventory data you are on your way to making more informed management decisions that ensure you are allocating resources as efficiently as possible.

While it is much easier and less expensive to build a map with existing data that requires some modifications than reshoot your entire inventory using a GPS device, moving forward we recommend you use a mobile mapping application or portable GPS device so that you can capture detailed location information at the time of planting, and don’t have to rely on a third party to maintain your database. We also recommend checking and adjusting tree locations as part of routine fieldwork. 

Run into snags following our geocoding instructions? Want to learn more about different mapping options? Drop us a line at opentreemap@azavea.com. We’d love to hear from you.

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