Fire Mapping in Google Earth™

Accurate, efficient, cost effective wildland fire mapping from a fixed wing platform.

Matthew Snyder

July, 2015

Introduction

In this document I will describe several methods for mapping wildland fires from a

fixed wing platform in a way that minimizes flight time over the fire. This will

reduce fuel cost and hazard exposure as well as make aerial mapped perimeters

more accurate. Mapping is done on the ground in a digital format that is easily

transferred into ESRI ArcMap for producing conventional paper maps.

Historically, large remote wildland fires have been mapped by an Aerial Observer

hand drawing fire perimeters on USGS Topo Quads. Mapping is done in the air

over the fire by flying numerous laps around the fire while the mapper draws in

what they see. This takes time and fuel and can be hard on the mapper due to the

possibility of motion sickness.

Perimeters are also collected from rotor wing platforms using a “GPS Sharpie”

method. This requires a much more expensive helicopter flight taking a GPS track

log. The pilot is required to slowly fly the entire perimeter at low level while

performing complex maneuvers in order to catch all fingers. This method takes

significant flight time leading to increased costs and increased exposure to

associated hazards. As well, accuracy is defined by the skill of the pilot.

Methods described use an Apple iPad™, but can be easily replicated with a regular

digital camera, GPS, and second computer monitor.

Method #1

In this method, called Photo Rectification, mapping is performed by comparing

aerial photography to landscape imagery in Google Earth and drawing in the fire

perimeter as a polygon. It is very important that you have enough quality imagery

encompassing the entire fire perimeter.

Photo Collection

Use of a GPS track log is advised but it is important to realize and pass on to your

pilot that you are not mapping using the “GPS Sharpie” method. Your GPS track

log will not be used for the perimeter. It is merely a broad reference for your

location when the photos are taken.

In drawing your perimeter in Google Earth you will be referencing the fire

perimeter to terrain and vegetative features. The more unique features you can

reference outside of the fire the better. In order to achieve this you will need to

have significant altitude and distance from the fire. I have successfully mapped

fires from as high as 16,000 feet to get the whole fire in the frame, but 4,000 to

5,000 feet AGL is usually a good altitude to aim for. A good rule of thumb is to

look for about a 45° angle. 5,000 feet up and 5,000 feet out from the perimeter

works well. Remember, you are not flying the perimeter and it is more important

to capture the unburned areas around the fire than the fire itself. Features to look

for are streams, ponds, meadows, and any change in vegetation, etc. The more

distinctive features in a single photo, the easier it will be to align and reference it

in Google Earth. You will want about 10% of the photo to have fire and 90% the

area around the fire. Take photos from multiple directions. Take lots of photos.

You will want plenty of overlap between photos. You cannot have too many. Un-

needed photos can be deleted later. Having to re-fly a fire to get missed imagery

is fairly counterproductive. Sufficient photos should be collected in one pass

around the fire.

Application

I use an Apple iPad for all my mapping. The iPad has a decent camera which uses

a built in GPS to geo-reference photos taken so you will know where each photo

was taken from. This will aid you in gaining a point of reference when drawing

them in Google Earth if you don’t have easily recognizable features in the frame.

As well, the large, high definition touch screen makes it easy to zoom in on areas

of interest in your photos.

I use an app called GPS Kit by

Garafa to keep a track log in the

background while I am taking

pictures with the stock Camera App.

Tracks can then be exported from

the app in .KML format and loaded

in Google Earth. If an iPad is not

available, tracks from Garmin GPS

units can be easily imported into

Google Earth. Tracks are saved in

.GPX format in newer GPS units. For

older units such as the 60CSx and

eTrex, tracks can be imported into

Garmin MapSource and saved as a .GPX. Google Earth has built in support for

these files. Simply drag and drop them anywhere on the map in Google Earth

from an Explorer window. Tracks are saved in internal storage in the

x:\Garimn\GPX directory. Remember to first save them somewhere on your hard

drive if you want to use them once you disconnect the GPS.

Individual photos can also be imported as waypoints using a free app called

Avenza PDF Maps. Some options have changed in the app so make sure you

update to the most recent version 2.5.1 or higher. Full use of this app is beyond

the scope of this document, but I will describe the process for exporting photos.

Ten fires were mapped during the above flight with minimal

turns over the fires.

In order to get your photos into a .KMZ file you must have a PDF map of the fire

area. USGS Topo Quads can be downloaded from the Map Store within the app.

As well custom map sets are available for most areas.

Select the map and use the wrench button to pull up the Tools menu.

Tap Plot Photos and tap on the photos of the fire that you just took. Only

photos that are geo-referenced in the bounds of the map you have loaded

will appear.

Tap to select the photos of the fire and tap the Done button when finished.

You will see your photos placed on the map as red pins. In earlier versions

there is a limit of four photos per import so make sure you update to the

newest version.

Tap the Map Features button in the lower right corner of the screen.

Tap the Export button in the lower right of the pop-up menu.

Under the SEND TO menu choose iTunes File

Sharing.

Under the DATA menu select Custom and

chose your Photo Library layer.

Under the MEDIA SIZE menu choose Small -

1024x768. This saves space on file size and

makes them much easier to view in Google

Earth.

Tap Export to finish and use iTunes File

Sharing to retrieve your .kmz file.

Load the resulting KMZ file into Google Earth and the photos will show up as pins

in their respective locations. Clicking on a pin will show the associated picture in a

pop-up window.

Zoom in to the fire area in Google Earth using the imported GPS track and

imported photos as a reference. Click the Add menu > Polygon. This will bring up a

new polygon properties window. This menu must be open to add/edit the

polygon for the fire. Add a descriptive name with the fire name/number and the

date the pictures used to draw the perimeter were taken. Example:

20150718_1300_599_FireName_Perim_YourName. Entering the date in this

format will keep it somewhat in line with GIS standards for export to ESRI

ArcMap.

Before you start drawing your perimeter, go to the Style, Color tab and set your

Line and Fill (Area) colors. For the initial drawing it may be easier to change the

Area drop-down from Filled+Outlined to Outlined. This will keep the fill color from

hiding areas while you are drawing. Alternately you can reduce the Opacity to a

level you can easily see through.

When drawing, find a photo with the fire perimeter near an obvious reference

feature. This may be a pond, a distinctive bend in a river, a meadow etc. Even in

areas of low resolution Landsat imagery in Google Earth you will be able to find

many of these features. Left clicks add points to the polygon, and right clicks

delete them. To add points in the middle of a line just select a point where you

want to begin adding and new points will be drawn from that location. Tilting and

spinning the camera to match your photos will make it easier to visualize where

the perimeter line should be placed. When you are done, click ‘ok’ to save your

polygon.

If you need to edit the polygon, right click it in the menu and go to ‘Properties’. Be

aware that the draw direction may have changed. With practice you will be able

to quickly make fire perimeters from photos.

Sometimes photos need some modification in order for the black areas to really

stand out. The Photos app in iOS can do amazing things with a hazy photo. Simply

select the photo, hit Edit, and tap the magic wand tool. By tuning diffferent colors,

contrasts, and balances of your photos you can make your photos much easier to

work with.

Much of Alaska and remote parts of the Lower 48 are covered in low resolution

Landsat imagery. Photo Rectifying fire perimeters with this imagery can be

difficult and takes practice to do with any accuracy. Thanks to the University of

Alaska Fairbanks’ Statewide Digital Mapping Initiative (SDMI) there is often better

imagery available. The SDMI - Best Data Layer is a KML overlay that brings good

high resolution imagery to may parts of Alaska. The layer can be downloaded

from http://wmsha.gina.alaska.edu/kml/bdl.kml.

Method #2

In this method photos will be added to Google Earth as Image Overlays. This

“drapes” the photos over the terrain replacing the stock Google Earth imagery

with imagery of the fire. This may not be practical in all situations due to

smoke/weather conditions obscuring parts of the fire. Once the Imagery is in

place, drawing in the polygon is very fast and very accurate.

Photo Collection

Photos must be taken from sufficient altitude to encompass the whole fire or

larger sections of the fire. Photos must have zero oblique, meaning they must be

straight down with no angle to them. While this may be nearly impossible in an

aircraft without a bubble window, this can be mitigated with an exterior mounted

camera taking frequent time-lapse photos. Some recognizable features must still

be present in order to align the photos with the background imagery.

Application

Using the track import method described above, find the area of the fire in

Google Earth. In the Add menu click Image Overlay. In the window that pops up

click Browse and navigate to the desired photo. The original placement will likely

be much larger that it’s true size on the ground. Resize it by dragging on the sides

and corners, move it by dragging from the center cross, and rotate it by moving

the green diamond. Play with the Opacity slider to make the background imagery

visible through photo. Take your time stretching and spinning the Image Overlay

with the opacity reduced until everything lines up. Once complete take the

Opacity slider back to full and hit Ok. If the fire is too big to get in one photo just

repeat the above steps with multiple photos until you have the whole fire. The

perimeter can now be quickly traced over the new Image Overlay by adding a

polygon as described in Method #1. If the polygon is not showing up because the

Image Overlay is hiding it, you can raise it up by clicking on the Altitude tab in the

polygon properties and setting a specific height Relative to Ground instead of

Clamped to Ground. 1-2 meters is usually sufficient.

Conversion to ESRI ArcMap

Once you have a completed perimeter you will need to convert it to a shape file

format that is recognized by ESRI ArcMap. You will need DNR GPS which can be

downloaded for free from http://www.dnr.state.mn.us/mis/gis/DNRGPS/DNRGPS.html.

In Google Earth right click on the polygon you want to save in the sidebar and

click on Save Place As… You can keep the name you gave it when you created it or

give it a new one. Make sure you select the Save as type: as KML not KMZ. See the

glossary at the end of the document for the difference.

Load DNR GPS and click the File menu > Load From > File… Change the file type in

the lower right to Google Keyhole Markup Language (*.kml). Navigate to the file

you just saved and let it load. If you don’t see your file, confirm that you saved it

as .kml not .kmz in Google Earth.

To convert it click the File menu > Save to > File… Change the file type to ESRI

Shapefile 2D (*.shp) and give it a name and hit Save. In the window that appears

select Polygon and click OK. This step is very important as ArcMap does not easily

convert from lines to polygons. DNR GPS will automatically create the four

necessary files that make up a shapefile.

Conclusion

As technology advances, tools are being produced that will allow us to become

more efficient in our daily activities. Mobile devices such as smart phones and

tablets have the capability to provide us with a vast amount of information, at our

fingertips. Products are becoming available that were just not possible even a few

years ago. I feel that it is important, as an industry, to keep up with these

advances. This is just one way that we can achieve this.

Glossary

DNR GPS – Windows PC Program

Windows PC program for loading data from GPS units and converting files

between several GIS standard file types. Example: ESRI .shp, Garmin .gpx,

Google Earth .kml, etc.

Google Earth Pro – Windows/Mac/iOS/Android program

Google Earth Pro is the more powerful and capable version of Google Earth

that has until recently required an expensive subscription. It has many extra

options over the standard version including showing measurements for

lines and polygons, native support for ESRI shapefile import, and improved

print and photo export resolution.

Google Earth Pro is now free. After you install and run it the first time it will

ask for your email and license code. Just enter your email and enter your

license code as GEPFREE.

GPS Kit – iOS App

Paid iOS App for recording GPS tracks and points. Data can exported in

multiple formats including KML and GPX. Developed by Garafa, LLC.

GPX – GPS eXchange Format

An Open XML language for storing geographic data for waypoints, lines,

and routes. Due to its open nature, any GPS manufacturer can implement it

without paying licensing fees.

KML – Keyhole Markup Language

A text based XML language for defining GIS location data for use in Google

Earth and many other programs. Data may include point, track, and

polygon data as well as photos, point descriptions, 3D models, web links,

etc. Files can be manually viewed and edited with any document viewer.

KMZ – Keyhole Markup Language - Zipped

A zipped or compressed KML file containing all associated images, icons,

overlays and 3D models.

Note: This is actually a .zip file. If you change the extension from .kmz to

.zip you can browse its contents like a normal .zip file. There will be a

doc.kml containing the normal .kml data and a \Photos directory containing

any photos associated with that layer.

PDF Maps – iOS App

Free iOS and Android App that uses a device’s internal GPS to show a user’s

location on a PDF format map. Points and lines can be created and

exported or imported on maps. Developed by Avenza Systems Inc.

SDMI – BDL – Google Earth KML Layer

University of Alaska, Fairbanks’ Statewide Digital Mapping Initiative (SDMI)

is a great source for good imagery in remote parts of alaska. The SDMI -

Best Data Layer (BDL) is a KML overlay that brings good high resolution

imagery to many parts of remote Alaska. The layer can be downloaded

from the Geographic Information Networks of Alaska (GINA) website at

http://wmsha.gina.alaska.edu/kml/bdl.kml.