How To Map Motus

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Zoom In to See Pukaruha and Reao Atolls

Reao Atoll FP - ISS004-E-12987, 12988, 12989 Images Modified (1:75,000)

For whatever reason Landsat ETM+ does not have a mosaic that covers Reao Atoll. Google Earth has Landsat imagery, but no imagery for this area at the NASA site where I download my Landsat ETM+'s. As I am making all of my maps without using DigitalGlobe imagery, because one day I might want to sell my shorelines, I must locate other imagery sources. The International Space Station (ISS) is a source of sometimes excellent imagery. And, in fact, ISS004 has 3 cloud-free, highly detailed images covering Reao Atoll, my current target project.

I downloaded, modified their sizes, constructed a "whole atoll" mosaic, rotated the image to align it with my base island shoreline vectors (NGA PGS vectors) and georectified this image using 7 GCPs.

Reao Atoll FP - Other Precision Mapping on ISS Images - Finished Motus (1:40,000)

Reao Atoll FP - Other Precision Mapping - Finished Motus (1:40,000)

Once I had a georectified image, my digitizing could proceed. I decided to map motus first, thus the title of this post. Motu mapping is quick, repetitive and gives one a sense of completion. Each motu is actually a small island. Reao Atoll will ultimately be made up of a 100 or more islands. The two above images show the results of about 2-hours worth of digitizing. I always strive for EVS precision, Landsat ETM+ resolution or better. This imagery allows me to exceed EVS precision. For mapping quality purposes, I label it as Other precision and label it's Source attribute as ISS-Hi Res. I have completed 58 Other precision island polygons. Let's look at the challenges one encounters as they map motus.

Reao Atoll FP - Other Precision - Digitizing Motu (1:10,000)

First, I am working at 1:10,000 scale. At this scale, I am able to maintain sharp feature clarity. In addition, this resolution allows me to make consistent shoreline determinations that will work with the scale of my finished map, between 1:50,000 to 1:25,000. My mapped shorelines consist of actual or suspected (based on color) above-water features. Sounds easy enough to consistently identify, but it isn't. After mapping a few thousand motus, I have learned to make a color(s) to shoreline decision and rigourously adhere to that definition. In imagery, color is god.

In the Reao Atoll image, the motu shorelines are identified as a white sand color. Having studied enough hi-res 1-meter imagery of reefs and motus, I know that between motus are features called hoas. These serve as channels allowing water to flow in and out of the lagoon. Eventually, these hoas fill up with coral rubble and sand, vegetation takes root and motus join motus to form a continuous land ring around a lagoon. Given enough time, the lagoon quite often fills in and, sea level cooperating, a flat island forms where an atoll once stood. Using my white sand color as my motu shoreline, I began digitizing.

Reao Atoll FP - Other Precision Mapping - Finished Motu (1:10,000)

If I do a good job, my project consists of a series of motu shorelines. The digitizing is monotonous, eye-straining and lately, my feet hurt because my chair is uncomfortable. But the finished map is what I work for. I'll share it with you when I've finished. Until then...

Enjoy!

Thoughts - Mapping New Britain PP

I was explaining my mapping work to a person I met at a party earlier today. This individual asked all of the right questions ( What do you do? Where do you get your images? How do you digitize the shorelines? What do you do with your finished maps?) Poor guy! I answered every question with a detailed, lengthy and somewhat technically boring response. After my fifth lengthy reply, he excused himself and joined another group.

As I reflect on my exchange with this curious person, I am amazed at the breadth of my knowledge and convinced that I can be very boring. I really do know quite abit about digitizing shorelines. After a few thousand kilometers of continental shorelines and 9,000 island shorelines, I am able to digitize a precise shoreline (within the limitations of Landsat ETM+'s 14.5-meter resolution).

Early on, I had professional cartographers tell me my maps would be useful at 1:125,000 to 1:63,500. I have learned that my island shoreline maps are useful at scales well-below these upper limits. I typically post completed maps at 1:25,000 scale. After adding layers of information, they work well for an individual attempting to determine a relatively coarse view of an island. Landsat is not DigitalGlobe's hi-res imagery, but it does a great job at giving one a highly resolved broad view of a geographical area.

New Britain PP - Digitizing from Landsat S-55-05_2000 (1:19960)

So, how is it that I do what I do? In digitizing, that is. The above image shows a typical stretch of large island shoreline. An attempt to generate vector shorelines from Landsat ETM+ was done a few years ago. This data, called NGA PGS, is fairly good at defining a shoreline, but coastal swamps are excluded causing some very strange looking maps of islands. If the island or shoreline contains water-innundated shoreline, NGA PGS does not map it. They could have, but someone, somewhere thought it would be good to exclude it. My shorelines include these water-innundated areas. The red line in the above image is my completed EVS precision shoreline. Except for the final vector which I purposely placed in the sea, the shoreline is much more accurately delineated than NGA PGS, WVS, DCW or any of the other available global shorelines. I am not saying EVS precision shorelines are global yet. I am an optimist. Someone, somewhere, sooner than later will fund my mapping efforts and the result will be a global shoreline at EVS precision.

Enjoy!

Thoughts - Changing Background Colors and Blend Options

The Effect of Blends and Backgrounds on LIIMs

I most often digitize from LIIMs using Global Mappers's Blend Mode called No Blend (Slide 1). No Blend shows the various land and water features as Landsat ETM+ mosaics intended them to look - somewhat natural. For most projects, this image works fine. However, atolls present some unique challenges - What is above water and what is below? What is shore vegetation and what is bare earth that looks like shore vegetation? Where does the land end and the reef begin? Like I said, unique challenges.

When I encounter these challenges, I use a couple of different options - 1) changing the background color to either Yellow (R-157,G-191,B-202), Pink (R-255,G-128,B-192), Light Pink (R-255,G-193,B-224) and Blue (R-157,G-191,B-202) and using two new Blend Modes - Difference and Color Burn. Let's talk about Difference first.

Tauere Atoll - Blend Mode Difference and Blue Background

Difference creates a soft looking false color image that makes certain atoll features stand out, for example the sand. It is also a great way to distinguish underwater features. I always switch between No Blend and Difference to visually confirm my work.

Tauere Atoll - Blend Mode Color Burn and Blue Background

Color Burn creates a sharp separation using false colors. The blue background and Color Burn allows for some potentially very precise digitizing of various island features. Using the other background colors, other than blue, gives a washed out effect. Not very handy for digitizing work.

My biggest challenge when working on an island mapping project is determining the shoreline - where the water meets the mostly dry land. Using the Global Mapper's Blend Mode and changing background colors is a great way to meet this challenge.

Enjoy!

Thoughts - EVS Precision Digitizing at 2-Kilometers per Minute

Nisida Ioura - LIIM From N-34-35_2000 (1:65,000)

So you've always wanted to hand-digitize an island shoreline. Your GIS friends tell you "No way! It takes way too long. And it's not as accurate as some of these slick black-box vectorizing software packages." You ignore them. Good for you!

First get you a good software package to digitize from. You all know where I stand - Global Mapper. You can always download and try their software for free. Just select my Global Mapper sidebar link and follow the instructions. Once you've got the mapping software loaded, it is time to get your base imagery. You can either download it from the NASA site or get in touch with me and I'll hook you up with imagery for your island.

Nisida Ioura - EVS Precision and GSHHS WVS (1:65,000)

Load the imagery into GM, zoom into a section of the shoreline where you will begin digitizing at a scale of 1:12,500, switch on Anti-Alias option in the Control Panel for your base image, select the digitizing tool, select the "Draw a Line" option and start digitizing. I like digitizing to music. This morning it was "The Planets" by Gustav Holst. I traced the above island's shoreline, listened to music and sipped a cup of coffee. I started at 5:50AM and finished Nisida Ioura's shoreline at 6:05AM - 15-minutes to digitize a perimeter of 30-kilometers - 2-kilometers per minute.

I always experience a satisfying sense of accomplishment when I complete an island's shoreline at EVS precision. I know that my island shorelines are as accurate as one can get using the tools I use. I have done enough comparisons to know that my shorelines can be used to create useful maps suitable for a wide range of activities.

If you want to make your own maps, just do it. Stop making excuses. Stop letting others tell you what you can or can't do. Go ahead and make your map. If your first one looks crappy, I promise your next one will look less crappy. And after a few years of making your own maps - you'll be able to say "Now, that's a nice map!"

Enjoy!

Thoughts - Why I Use Global Mapper to Digitize My Island Map Projects or 30-Seconds From Start to Digitizing

Step 1 - Drag, Drop and Load LIIM (5-Seconds)

Let's keep this simple. First I locate the georectified island image I want to work with. This is Nisos Pelageos LIIM. I merely drag the icon, drop it onto Global Mapper (GM) and it loads. The entire step took 5-seconds.

Step 2 - Before Applying Anti-Alias (8-Seconds)

Step 2 can happen when the image is at full view. I zoomed in to show you why I use the Anti-Alias effect (smooths pixels). The above image shows the square pixels. In my opinion they are clumsy to work with. I will smooth them out with the Anti-Alias effect. I select the image through a menu item.

Step 3 - After Applying Anti-Alias (2-Seconds)

Once the image is selected and the Anti-Alias effect is switched on, I end up with smoothed pixels. They are much easier to work with for the purposes of my maps. Steps 2 and 3 took 10-seconds.

Step 4 - Zoom to 1:12,500 to Begin Digitizing (10-Seconds)

I like to work at 1:12,500 scale when I digitize from LIIMs. Depending on my expectations, the clarity of the image and other factors, I will sometimes work at larger scales to obtain my EVS precision mapping. Zooming takes 10-seconds. Most of that time is spend zooming in on the correct portion of the image.

Step 5 - Select Create New Line (5-Seconds)

In Step 5 I select the digitizing option and right click to select the specific function. I work primarily with polylines, so I select Create New Line. That takes 5-seconds.

Step 6 - Digitized Line (Polyline)

Now comes the fun part, digitizing the shoreline or whatever layer of information you wish to work on. Digitizing with GM is tracing a consistently defined shoreline. That's the tricky part. That part takes lots of practice. But from load to digitizing - that only takes 30-seconds with GM and that really makes me happy.

Enjoy!

Thoughts - Global Mapper, Mike and Excellent Customer Service

First about Global Mapper (GM) and why I use it. My work on islands is all about loading very large raster images (Landsat ETM+ mosaics). Each file is 100 to 300 MBs in size using MrSid format. Them is some big files! GM makes loading these very large files a snap. I select the file and it's loaded within seconds. I might add, properly georectified as well. Some of my projects require multiple Landsat images. No problem. I believe the largest file that can be handled by GM is up to 4 GBs.

Once I have the images loaded, I begin digitizing. Again, it's a snap. Digitizing in GM is precise and extremely flexible. After a brief learning curve, one is digitizing to their heart's content. Once the various layers of information have been created, the export choices are numerous.

Now my favorite part about the GM product - Mike. Mike is Global Mapper. I don't know if this is actually the case, but I visualize Mike working out of a small office. His phone isn't ringing, because he does all of his customer interaction via the web. He works daily with customers tweaking his excellent mapping program. Many times I read within the GM group that a customer wishes that something could be added, or a portion of the GM program adjusted, or a process simplified and most often within minutes to a few hours, Mike makes the change and posts the improved version of the program for all clients to retrieve. For this service, which is unparalleled in the industry, he charges nothing. He wants his product to be the best it can be and he knows that it is ultimately the end-user that is the best source from which to learn how to improve his program. If he can make the change, he makes it. If the change requires extensive programming, he makes the change more slowly, but he makes it. If the change is beyond his vision of what his program should be, he will provide you with a work-around or tell you straight that he isn't able to make the change. Mike does what every business should do - listen to the customer and respond quickly with a solution, not a promise of a solution, but a finished solution. Mike is the best!

I have other mapping software, but when I call them for answers, they want to charge me. If I work with them online, they give me happy talk about my question and they definitely do not make changes to their program in realtime. Most often, they tell me why something can't be done. Whereas, Mike just makes the change and provides the updated program to you.

All of you folks in charge of a product or service, LISTEN UP! Here is how Mike does his business and how you should - He reads your request. He answers your query. He adds to, changes or adjusts his program to satisfy your request. He makes the changed program available to his clients. All of this at no charge, and typically done the same day. And for his efforts, he has an extremely loyal and growing customer base.

That's good business! And that's why I continue to use GM.

Enjoy!

PS - GM is still my favorite mapping product for my type of projects and Mike is still the greatest when it comes to quality customer service.