Building a Map with UAS Data

Introduction

Why are proper cartographic skills essential in working with UAS data?
In order to create a functional map, one needs cartographic skills. To create maps by using UAS data, images, these skills would be applied to ordinary images of a particular area. For the user to interpret the map properly, cartographic skills are key.

What are the fundamentals of turning either a drawing or an aerial image into a map?
Every map should have a North arrow, a scale bar and a mini locator map of where the area is situated. Also, a watermark of the map's creator and relevant metadata like what sensor took the images would be appropriate information.

What can spatial patterns of data tell the reader about UAS data? Provide several examples.
Information about elevation is perhaps the most obvious spatial characteristics the user could retrieve from UAS data. One can find ridges and variances of height by managing UAS data properly. Also, distances are to be considered as a spatial attribute, that is objects location in relation to each other. Using hyperspectral sensors that give information about spectral classes to objects is another example.

What are the objectives of the lab?
The main objectives of the lab were to get a basic understanding of map creation with UAS data. We used ArcMap to create maps but was also introduced to ArcScene, which is a software tool for creating a scene over an area of interest. We tried to fly over it from a birds perspective.

Methods/Lab Assignment

What key characteristics should go into folder and file naming conventions?
Dates, names of locations, what kind of om digital model is used and file extension is key for naming files. Also, keep the filename without spaces. For instance: "20170613_wolfpaving_dsm.tif"

Why is file management so key in working with UAS data?
Working with UAS data means a lot of files. Good file organization is heavily aligned with the effectiveness of the user.

What key forms of metadata should be associated with every UAS mission?
Examples of UAS metadata could be; flown date, pilots name, UAS platform, sensor type, altitude, Ground Control coordinates, and UAS coordinates.

Create a table that provides the key metadata for the data you are working with.

Figure 1: Metadata

What base map did you use? Why?
I choose to open a Topographic map cause my goal was to choose an easy-navigated map. I thought that maybe choosing a map, which displays streets in an easy manner could be good.

Build Pyramids and Calculate Statistics for each data set. What is the difference between a DSM and DEM? Digital Elevation Model (DEM) often used as a generic term for Digital Surface Model (DSM) and Digital Terrain Models (DTM). Elevation refers to height above a given level, particularly the sea level. A DTM is an object scraped digital model, where the surface refers to the earth, that is ground without buildings, trees, and other vegetation.

DTMs are LiDAR-derived and with LiDAR (3D laser scanning) it is also possible to create another type of DEM by filtering out objects on the surface. This is how the so-called Normalized Digital Surface Model (nDSM) is created. To put it in other words, DSM - DTM = nDSM, or the height of objects standing on the surface of the earth.

Figure 2: Differences between various DEMs and the creation of an nDSM. Courtesy to Tiramisu.

ArcMap

Figure 3: Statistics of the Wolfpaving mosaic. These values represent pixel values, which goes from 0 til 255. It has four bands but since the fourth is transparent, only three will be relevant.

Figure 4: DSM of Wolvpaving. This represents height values.

I generated a hillshade for the DSM layer, the difference is displayed below. One can see there is a decent shade effect from a distance, but when zooming in it is not that great shading quality.

Figure 5: DSM without hillshade effect

Figure 6: DSM with hillshade added

In order to have better hillshade effect, using a so-called hillshade tool is common to use in conjunction with a DSM model.

Figure 7: This is rich and robust data set where it is much easier to see details.

Figure 8: Same data set, zoomed in.

Figure 9: Swipe tool applied to the DSM and orthomosaic data sets. to display differences.

Setting the transparency for the orthomosaic data set (in my content pane, the layer above) to 45%, we get the best from both worlds.

Figure 10: A nice hillshade effect integrated with the elevation features.

ArcScene

In order to remember some of the functions we learned in class, I will put some hints and traces below.

Figure 11: From properties and the Base height tab we access "Floating on a custom surface"-feature. It's where all the raster values from the DSM-model are assigned to their elevation values.

Figure 12: The rendering is giving shading to where the topography top a lot more.

Figure 13: A 3D rendition of the data set we created in ArcMap.

Figure 14: From the data frame properties, it is possible to extract the elevation values.

Figure 15: The result of the exaggeration, I just made. Settings at about 2.4.

What is the purpose of vertical exaggeration? What settings do you have for your data?
The reason one use exaggeration is basically to demonstrate elevations differences. After some playing with the values, I decided to go for exaggeration value as 1.

What color ramp did you use? Why?
I was elaborating a lot here but finally, came to the conclusion to use the Red-to green diverging color ramp. This was cause I like red to display the tops and green to represent the lowest areas. That said, if there would have been water in our data set I may have chosen the Spectrum-Full bright color ramp in order to have blue to display the bottom part of the scale.

What are the advantages of using ArcScene to view UAS DSM data vs. the overhead shaded relief in ArcMap. What are the disadvantages?
ArcScene is a great platform for visualizing 3D data and elevations are much easier grasp. Another advantage over ArcMap is that ArcScene is better for exporting 3D-models. One disadvantage by using ArcScene is that is is mainly for small study areas, wheras ArcMap is better of handling bigger geographical areas.

Find a zoom setting and angle you like in ArcScene and export the image as a jpeg or file of your choice. Is this export a map? Why or why not?

Figure 16: This image export from ArcScene is not a map. It does either contain the direction of North, a scale bar, a locator map, metadata nor does it contain a watermark.

Building Maps

This section demonstrates map creation done in both with an orthomosaic image and a Digital Surface Model image as a base. An orthomosaic image is an aerial photograph that is geometrically corrected so that the scale is uniform. An orthomosaic image can be used to measure true distances because it is an accurate representation of the earth’s surface.

Figure 17: Orthomosaic map over Wolfpaving.

Figure 18: DSM Map over Wolfpaving. This looks like a DTM but is actually a DSM, taking in Nadir viewing.

Conclusions
UAS Data gives the cartographer and GIS user a variety of useful options to shape his or her map for whatever intention. UAS can be used both professionally but can also for used under more private circumstances.

The data that comes from UAS is raster values which brings some limitations. Another huge disadvantage, especially when working in 16 bit ArcMap is the long processing time. Zooming in too close could cost the user a lot of time. I know.. Zooming with scroll button on the mouse is not the preferred way to go ahead, instead of using the zooming glass feature and try to be as specific as a possible help. Finally, other areas mapping and UAS data could be a useful tool is for security issues and searching operations, e.g. for missing people.