Quercus arboretum

Here is a detailed description of the steps taken in using a combination of Google Earth and GardenCAD (vector based CAD software) to create a system to manage an arboretum consisting primarily of Quercus spp.

Step 1.

Load Google Earth and zoom and create a low resolution view of the site containing the arboretum. Save several images at the same magnification taken by Google Earth. Give them meaningful names. The images below show a sequence of Google Earth images from 2002 to 2011.

Low resolution arboretum 2004 arboretum

2009 arboretum 2011 arboretum

Substantial reforestation has occurred over this period of time. Note the growth of the woodlot in the lower right hand corner of each image. This is one of Google Earth's real strengths; it can monitor changes over time. The two figures below shows the woodlot in 2002 and in 2011 and clearly demonstrates the rate of growth.

Arboretun 20011

Movie  Here is a link to a YouTube movie that shows how this is done.

Interesting as the above is, the client wishes to use our CAD software to record more detailed information about individual species in an arboretum that forms part of this site. In other words, he wants to use Google Earth as a backdrop and aid to location of individual plants in his CAD drawing.

ip  Raster images such as the screen grabs above can be pasted into our CAD software and scaled such that the images is registered and will report back true distances (see other article).

Step 2.

Load each image into its own layer and scale appropriately. The figure below shows the Google Earth image in our CAD software with the distance command being used to check the registration of the image against the value supplied by Google Earth


A distance of 137 meters reads 274.248 in our CAD software so the images need to be scaled by 137/274.248 (0.499) for registration of our screen grab to Google Earth. The figure below shows that has been achieved. We can now make enquiries of our drawing that mean something on the ground.


Step 3.

The arboretum. The client wants to capture and record information about his Quercus arboretum. The image below shows that we have used a polyline to indicate that area and also added a local grid for easy reference. Later when we add a symbol to the drawing, we can add a local grid reference.


Movie  Here is a link to a movie that discusses the delineation of the arboretum and a calculation of its area.

Step 4

Add plant data. Insert block with attributes and store non graphic information.

Movie Here is a link to a movie that shows how lots of valuable non graphic information can be stored with the drawing. It is now a database that can be used to monitor development and management of a plant arboretum.

The image below shows the data in an early stage of development. We have selected a tree marker block and ''

'popped up' the Properties block. 10 different attributes have been used to store information about the highlighted tree.Properties Quercus alba

Step 5.

Create and set up a Page for each species. The figure below shows a page for Quercus alba showing a habit and close up of the fruit.

Page for Quercus

Use the Pages command to return to model space - the design space.

pages palette

Back to model space


Some fine adjustment of the position of the Google Earth images may need to be made if comparisons between years are required. Do remember that the limitation here is the resolution of the images - probably 5 meters at best!

Entering information captured on the ground

The owner of this arboretum is more interested in keeping accurate data about his plants than examining Google Earth images and wants to start updating information in the CAD drawing. For that, he needs to stop relying on Google Earth and start accurate on-site measurements.

The simplest approach to this so-called 'ground truthing' would be to by stand next to individual trees with a hand held GPS, a notebook computer. Record the location of the tree - code in the GPS (unique identifier using integers) and record the GPS data and entering directly into our CAD marker block.

Note that each entity in a CAD drawing has a unique identifier value associated with it and (using that information) it is possible to zoom into that plant. GPS coordinates could be stored in the User Data field under properties.

Quercus arizonica

The coordinates of the sample point (way point) would of course be stored in the GPS. Returning to that point in future would be a simple matter of loading the GPS coordinates and tracking to the required point at the base of the tree.

Our marker has been designed to stores much data about a tree species (turkey Oak in this case) as shown in the figure below. We have also used the SCALE command to increase the size of the marker to match the canopy diameter. In this way, the relative size of the tree can be seen at a glance.


Permanent mark

It might be useful as a secondary check, to is to set up a permanent mark on the property for subsequent use by a survey team. They would be able to peg a much finer grid on the ground. The image below shows a 5x5 Meter grid with its corner point located on a permanent mark in the upper left of the arboretum area. Now, when a tree needs to be accurately located and a GPS device is not available

5 meter ground gris