Wednesday, January 07, 2026

Using iMap to record invasive plants: Web Version
Fairfax Tree Rescuer PRISM 

Feel free to practice using your own residence. Just delete the observation when you are done. 

In general, you are likely to find the web version easier to use than the mobile apps. It only has one flaw: when you zoom down to your location, it takes a while for the data to load. This is annoying. Once you get there, though, it works very well. 

1. Set up your iMapInvasives account using the web version.
You must be an official “member” of Fairfax Tree Rescuers for us to be able to use your data.

2. Take photos of the infested area 

3. Log on to iMapInvasives. Zoom to the approximate location. 

4. Choose the map display you prefer under Change Basemaps (upper right). 

The topographic version shows property lines (except in the cities of Fairfax and Falls Church). The satellite view shows the vegetation.  

5. Click on “Create Record: (upper middle) and follow this sequence.

  1. Presence
  2. Choose Point, Polygon, or Line, then click on the map to create the location. To create a polygon, click around the area you are surveying, dropping as many points as you need to capture the shape until you close the loop.
  3. ‘Next’
  4. Enter the species. 
  5. Tagged Project - Please use the relevant code below. You may enter multiple codes.
  6. Upload at least one photo. Note that if you click on “info” for a photo that you have added to Google Photos, it gives you a map with a marker for where the photo was taken.
  7. Add information about distribution, and (for polygons) the percent cover (see below)
  8. ‘Close’ 

6. Edit if you need to

  • Click on the observation on the map. 
  • Details (lower right)
  • Edit (upper right)
  • Add any comments or any other details you like. This first screen has all the features listed above. Clicking on “Go to Searched Area page to enter/view more information” brings up other, optional fields.
  • Save

Note: the program times out pretty quickly, but it will still look as if you are logged in. If it doesn’t seem to be working properly, log out and log back in again.  

Data we need every time

  • Project tag(s) (see below)
  • A point or polygon. Polygons allow us to better quantify the range and extent of an infestation, so please use them when you can. If you are using a point, make a note about the approximate size of the affected area.
  • Presence Records - the name of the species, and at least one clear photo. (If you had forgotten to take photos, you can proceed if you are 100% sure of the ID.) Ideally, include a photo that shows the extent of the infestations as well as one or two photos that allow reviewers to confirm the identification. When photographing the extent of the infestation, you might want to designate a location where you can include a landmark (or even place a marker) and return year after year to see progression. 
  • Distribution and (in the case of a polygon) Percent Cover 

One species at a time

Please create separate records for each species. iMap will give you other options, but they can be confusing to use and may confuse our data as well.

If multiple species are present in one severe infestation, such as trees blanketed by vines, choose the most dominant species and use the comment blank to note other species. If you prefer, you could create overlapping records for each species. 

When you are in the field

The only required thing to do in the field is take photos. Please try to make them clear enough for someone else to identify. DO NOT TAKE PHOTOS FROM A MOVING CAR UNLESS YOU ARE A PASSENGER! None of this is worth taking any risks. 

The mobile app is helpful when you want to drop a point or polygon somewhere in the middle of a park where you can walk in, do a quick observation, and be done. Otherwise, doing it from home on a computer may be easier and probably more precise if you are drawing polygons. Those are usually a bit of a guess anyway, and drawing polygons on a tiny screen is difficult. 

Project tags: All but the last four ‘projects’ (tags) are used to indicate property ownership. The last four are for severe infestations.  

  • 1625  VDOT rights of way - all
  • 1626  VDOT rights of way - inaccessible to volunteers
  • 1634  City of Fairfax Parks
  • 1633  Clifton, VA parks including CBA
  • 1629  Commercial properties
  • 1630  Fairfax Board of Supervisors land
  • 1635  Town of Herndon parks
  • 1637  Town of Vienna parks
  • 1640  Faith communities
  • 1636  Falls Church, VA parks
  • 1627  FCPA properties
  • 1632  FCPS (Fairfax County Public Schools)
  • 1628  HOA common land
  • 1631  Multi-dwelling unit common land
  • 1638  NOVA Parks
  • 1639  Single family home properties
  • 1642  National Park Service (NPS)
  • 1643  Military
  • 1644  Railroad rights of way
  • 1645  Federal lands
  • 1646  State parks
  • 1647  Severe vine infestations
  • 1685  Severe tree infestations
  • 1686  Severe shrub infestations
  • 1687  Severe ground-level infestations
  • 1690  Search for severe infestations
  • 1692  Operation Stream Shield
  • 1693  Severe invasive plant infestations

Percent cover

Unless it is 100%, this will always be a rough estimate. Keep in mind that you will be indicating a percentage for the entire polygon, even if that includes playing fields or other places with no habitat. This graphic might be helpful for visualizing percentages.