Thermal Imagery Collection

Introduction

The purpose of the weeks assignment was to collect the data for my final project which is based off my project proposal. We flew flights at three hours intervals collecting thermal imagery with the UAS platform. The first three flights and the last flight of the day were conducted with Mr. Mike Bomber, Dr. Joseph Hupy, and myself. We were joined for the 3:00 pm flight by the rest of the UAS class who were collected additional data for their own purposes.   Additionally, I collected in situ surfaces and soil temperature values immediately following the flights. The following blog post will display the methods we utilized to collect the data.



Methods

The collection of data started at 6:00 am on 4/18/2016 (Though the first flight did not get launched till shortly before 6:30). The same process was completed every three hours for a total of 5 flights and temperature values collected. I utilized the Matrix platform fixed with the thermal sensor we have used in previous lab exercises. I created a flight mission which covered my study area thoroughly while maintaining a short enough flight time to complete the mission in one flight. Dr. Hupy laid out 6 portable GCP markers and collected their locations with the dual frequency GPS in hopes of being able to see them in the imagery (Fig. 1).

Collecting surface and soil temperature values was the second step of the process. I determined my sample location prior to the first flight (Fig. 1). My sample sights were based on varying surfaces.  The surfaces included:

• Blacktop
• Mowed Lawn
• Prairie Grass
• Garden area with straw covering the soil
• Garden area with woodchips & straw covering the soil
• Wooden deck surface
• Roof with asphalt shingles
• Conventionally tilled farm field
• Wood chip pile
• Raised garden bed soil not covered

(Fig. 1) Display of the GCP marker locations and the temperature sampling locations in the study area.

I collected surface temperatures immediately following the completion of the flight utilizing an infrared thermometer (Fig. 2). Simultaneously, I collected soil temperatures from the same location utilizing probe thermometer. I will be utilizing the surface temperatures to calibrate the image values to display the temperature change of the surfaces throughout the day. I hope the soil temperature values will display the correlation to soil coverage and the reduction of temperature values.

(Fig. 2) Thermal infrared thermometer utilized to collect surface temperature values

Results

The final results have not been produced yet. I have completed the first step of creating a mosaic image in Pix4D software (Fig 3).  The remainder of the research will be conducted in the up coming weeks.

(Fig. 3) Display of the mosaic image from the 12:00 PM flight.

Litchfield Mine GCP Placement 4/11/2016

Introduction

The purpose of the class on April 11th was to place permanent GCP's at the Litchfield Mine site. Our professor Dr. Joe Hupy recently was awarded the Regent Scholar award from the University Wisconsin System Board of Regents'.  The award is to facilitate exploration in assessing inventory of aggregate mines. Dr. Hupy created a partnership with The Kraemer Company to access a aggregate mine site near the city of Eau Claire.  The access will allow Dr. Hupy and the researchers to continually fly UAS missions to assess the stock piles of aggregate materials at the site. GCP's are one of the components required for the accuracy needed to complete volumetrics of the aggregate piles. The goal was to place the GCPs all around the mine site where they will remain visible for all future flights.

Methods

During last weeks class time we built our own GCP markers.  Dr. Hupy purchased 4 ft by 8 ft sheets of 1/4 inch thick black plastic. We cut the sheets down to 2 ft by 2 ft squares.  We then cut a triangle out of a piece of plywood which was the same size at the plastic.  The triangle was used as a stencil to create the GCP point in the middle of the sheet (Fig. 1).

(Fig. 1) Plywood with triangle cut out laid over top of the black plastic 2x2 plastic sheet.

We then used florescent green spray paint to color in the triangle.  After letting the first side dry we flipped the plywood sheet the opposite direction to create and "hour glass" shape on the sheet (Fig. 2). Additionally, we added letters to each marker for data tracking purposes. The last step was to drill holes in the corners for anchoring purposes.

(Fig. 3) Completed GCP marker with painted triangle and letter.

Now we had to place the GCP markers.  We met at the Litchfield mine in the afternoon of 4/11/2016. We were met by a representative from Kraemer to help us select appropriate locations to place the GCP markers which would not impede their production operation.

After placing and anchoring the marker we utilized a dual frequency GPS to collect the location (Fig. 4). We completed the same task for all of the place GCP markers.

(Fig. 4) Collection of the location of the GCP marker using the dual frequency GPS.

Results

(Fig. 4) Display of placed GCP Markers at the Litchfield mine site.

Project Proposal

Introduction

The research for the project will focus on the use and functionality of the thermal sensor. The thermal sensor does not produce true temperature readings for ground surfaces. I hope through the collection of in situ temperature data from various surfaces on the ground immediately after the flight will allow calibration of the temperatures from the imagery. The main objective for the project will be to observe temperature changes of various surfaces throughout the day.  The research project will apply to future studies for applied agriculture land management. Observing surface temperatures for various land covers will add to the knowledge of land managers.

Study Area

The project study area will take place on property east of Fall Creek, WI.  The area has a variety of surfaces including, house, blacktop driveway, no-till garden, prairie grass field, conventionally tilled farm field, and maintained lawn.

Methods

The project will have the researchers collecting imagery and temperature readings at 5 different times of day.  The flight times will be as follows:

• Sunrise
• 8-10 am (Variation depending on sunrise time)
• Noon
• 2-4 pm (Variation depending on sunset time)
• Sunset

Before the flights occur the researchers will layout and survey locations to obtain temperature readings from various surfaces. The surface temperatures will be collected using an infrared thermometer. 

The process for all 5 flights will be the same. After preparing the UAS for flight the researcher will collect temperature readings from all of the monitoring locations. The flight will be conducted immediately following the collection of the temperature readings.

Discussion

The observations I am most looking forward to seeing are the differences between the various vegetation types on the property. Research has shows bare soil to have a considerably higher temperature compared to non-tilled soil with some form of cover crop or mulch. The temperature variation has an effect on the moisture contained with in the soil thus impacting the ability for plants to grow and thrive. I believe the results will show a noticeable temperature difference between the maintained lawn, garden, and prairie grass field.  Additionally, the amount the temperature increases throughout the day will display interesting qualities about the various surfaces.

Conclusions

Litchfield Mine--03/13/2016

Introduction

Today for class and we headed out to the Litchfield Mine in Eau Claire, WI.  Our class intended in collecting GCPs for a series of flights to be flown by Peter Menet of Menet Aero.  The objective of the flights was to calculate new stock piles of various aggregate piles from the mine site (Fig. 1).  

(Fig. 1) Aggregate piles within the Litchfield Mine Site.

Due to an unforeseen issue with the GPS we intended to collect the GCPs with we were unable to gather any GCPs for the site.  In the future our class will be exploring calibrating these images with previous images which were captured with GCPs to see if we can obtain the same accuracy without collecting GCPs every flight.  

Methods 

The flights were conducted by Menet utilizing his DJI hexacopter (Fig 2).  The hexacopter was rigged with Sony ILCE 6000 digital camera (Fig 3).

(Fig. 2) DJI hexacopter owned by Menet Aero.

(Fig. 3) Sony ILCE 6000 rigged on the DJI hexacopter.

Menet flew 3 different missions to assess the results of flights with various heights and quality of images. Menet flew the flights with the following parameters.

• 200 ft elevation and 12 megapixel resolution
• 200 ft elevation and 24 megapixel resolution
• 400 ft elevation and 24 megapixel resolution

The missions were created utilizing a mission planner software created by DJI (Fig 4).  The DJI software is very similar to the Mission Planner software which I have utilized in past blog post.

(Fig. 4) DJI mission planner software with one of the flight plans open.

After all of the flights were conducted I input the collected data in to Pix4D and created an orthomosaic image for each of the flights.

Results

( Fig. 5) Zoomed in image of the results from the 12 MP and 200 Foot elevation flight.

(Fig. 6) Zoomed in image of the results from the 24 MP and 400 foot elevation flight.

(Fig. 7) Zoomed in image of the results from the 24 MP and 200 foot elevation flight.

Additionally, I wanted to compare the results of volumetrics of a stock pile between the images. I utilized the volume tool in Pix4D to calculate the volume (Fig. 8).

(Fig. 8) Way points from Pix4D to calculate volume from.

(Fig. 9) Display of the volumes taken from all three images. 

Discussion

From examining Fig. 5-7, I feel the 24MP image collected at a 200 foot elevation had the best image quality.  The 12MP image collected at a 200 foot elevation had the second best image quality.  The 24 MP image collected at a 400 foot elevation had the worst image quality of the three. While image quality is one aspect I was examining, I am also taking in to concideration the amount of time it takes to process the image.  The initial processing times in Pix4D are as follows:

• 24MP (200 ft) : 1 hour 25 minutes and 15 seconds
• 24MP (400 ft) : 32 minutes and 21 seconds
• 12MP (200 ft) : 39 minutes and 2 seconds

I was hoping to keep track of the full processing time between all three of the images.  Unfortunately, my schedule did not allow me to babysit the computer to track the full processing time of any of the images. So my judgments will be based off the above processing times.  I feel the 12MP @ 200 ft has the ability to be the go to set up depending on the application.  Obliviously, the 24MP @ 200 ft offers a better resolution. Most applications will not require the resolution of the 24MP for the desired results of the project.

Conclusion

You will need to consider the desired out come for your project when deciding on what the quality of your imagery should be.  Each sensor will result in different outcomes.  Testing your specific platform and sensor will give you the best knowledge for selecting the best parameters.