lab 4

Introduction
In this lab we used ArcPro to make a orthomosiac, we were given instruction by Dr. Hupy. We followed along which was pretty helpful, it wasn't too hard to make but it did take a time to do the processing. We were unable to add the GCP's (ground control points), as they caused ArcPro to crash.

• What is photogrammetry?
• Accurately measuring objects and surfaces from pictures and other digital images.

• What types of distortion does remotely sensed imagery have in its raw form?
• there are a few different types of distortion, there is geometric distortion such as  lens distortion, perspective distortion,earth curvature, radial displacement, and scanning distortion. The distortion can be affected by the camera or sensor that is being used, or even the lens.  Another distortion can be caused by tall objects that when the sensor flys over the photos caught the sides of the object instead of a perfect birds eye view
• What is orthorectification? What does it accomplish?
• It is a way the the image can be corrected for errors like distortion. This makes the Image usable as a map as it is now accurate.
•  What is the Ortho Mapping Suite in ArcPro? How does it relate to UAS imagery.
• Its a set of tools in ArcPro that allows for orthorectified images from UAS or satellite imagery. UAS imagery that is taken straight down can be meshed together for revision and change detection.
• What is Bundle Block Adjustment?
• Its calculating pixles where they are at in space and corrects them to corrolate with eachother. 
• What is the advantage of using this method? Is it perfect?
• it minimizes error created and makes the best statistical fit for all the images.  But it is not perfect the points with high residual error are either repositioned or deleted.

Methods

• Files names should include important information in order to allow user to tell them apart. You should inlude things like dates, times, places. If multiple runs where done is a same area or if multiple files are similar in nature the should be placed in a file that identifies the similarity.
• File management is also very import to be able to find the proper files. This depends on the person but things such as being alphabetical or based on dates allows the user to find the files or folders in a quick manner and double check the correct data.
•   Metadata such as date flown, UAS platform, sensor, altitude captured, ground control GPS, coordinate system, and weather conditions should be included with every UAS mission. The data below is how it realates to the flight we analized.
• Date Flown:                             Nov 8th, 2018
• UAS Platform:                         Yuneec H520
• Sensor:                                    Yuneec E90
• Altitude Flown:                        70m
• Ground Control GPS:              Propeller
• Ground Control Coordinates:  NAD83(2011) UTM Zone 16
• UAS Coordinates:                    WGS 84 DD
• Pilot:                                         Joseph Hupy
• (figure 1) as seen in figure one this is just laying out the orthomosiac which took about 3 minutes

Figure 1

• (figure 2) figure 2 is after doing the bundle block adjustment which took an hour and 6 minutes to complete. normally GCP's would of been added before this step but we didn't do that in this lab.

Figure 2

• (figure 3) this is the same image as figure 2 but with the othro shown over it

Figure 3

Results 

• The map as seen in Figure 4 is a decent map, i left the UAS flight on for referance on how the photos were taken but looking back it would of been better if i would of removed them and made it look closer to a nice map. the image isnt perfect ether as the corners of the map have a lot of errors where the trees where stitched together. Overall the important parts of the map which are the in the center look really well and came out as a really nice map. 

Figure-4

Conclusion 

• The Orthomosiac tool is very helpful as it allows they user to take a large number of photos from an area and mesh them together. The tool takes what would be days or weeks worth of work on your own and makes it in minutes or hours.
• Summery, you take a few hours of flight to retrieve the needed data and then a few more hours of using ArcPro to process the data. In the end the user has a usable and accurate map. 
• The higer resolution DSM such as from LiDAR will make it more accurate as the LiDAR is able to pick up more data and more data points, this allow the image to be a higher resolution and be more accurate in elevation. The problem comes from the amount of time it takes to complete as by the time its done processing the data is already old and inaccurate.