Thoughts - When is a Shoreline a Shoreline? A Continuing Discussion.

Kyra Panagia - EVS Compared to NGA PGS

Comment posted by Anonymous:

Shorelines are usually created through stereoplotting or derived from surface models - rarely from monoplotting like you do. The problem with monoplotting is that your shorelines will be different depending on the tide, so your shorelines might very well be even more off in many places - especially at relatively flat areas and/or shallow water.

My response:

Anonymous, your observation concerning the use of stereoplotting and surface models providing an accurate approximation of a dynamic shoreline are well taken. If one had the imagery depicting the shoreline at various stages of tidal fluctuations during a set period of time, the methods you refer to would always provide the superior shoreline representation. However, after monoplotting 1,000s of kilometers of shorelines and comparing my EVS precision shorelines to NGA PGS precision shorelines - EVS shorelines track the Landsat ETM+ imaged shorelines more consistently then NGA PGS precision shorelines. My guess is that their method introduced unanticipated stutters, inconsistent shoreline identification and non-inclusion of water inundated areas.

EVS precison is not perfect, just better at tracking the visible shoreline more consistently then NGA PGS.

Comparison - EVS to NGA PGS, One More Time

Kyra Panagia - EVS Compared to NGA PGS

Enhanced Vector Shorelines are derived from Landsat ETM+ mosaics. When I carefully digitize an island shoreline using Landsat imagery as my base image, I create EVS precision vectors. This name describes an improved shoreline over World Vector Shorelines.

The NGA Prototype Global Shoreline claims to be a global vector shoreline derived from Landsat ETM+ mosaics, the same imagery I use. When I first learned of it, I thought to myself, "My work is done! MDA has produced the ultimate global vector shoreline. Well, they really haven't. It seems that their shorelines do not track Landsat's imaged shorelines. They are close, somettimes very close. But far too often, they are off, sometimes by 100's of feet.

It is my contention, if Landsat provides a clearly imaged shoreline, the vectors that describe that shoreline should be as close to the shoreline as possible. NGA PGS does a pretty good job, but when I compare their product to my EVS precision shorelines - mine are better at tracking the Landsat imaged shoreline.

Enjoy!

Thoughts - Zooming Futuna Island, Just For The Heck of It!

DigitalGlobe Imagery of Futuna Island Taken From Google Earth

Nothing special in mind. Just thought I'd zoom in on Futuna Island from 1:48,000 scale down to to 1:750.

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!

Data - World Port Index Data to Download and Correctly Plotted

World Port Data with Southern Hemisphere Data Misplotted



World Port Data Showing Attributes



World Port Data with the Southern Hemisphere Misplots Corrected

I hate to mess up, especially when it comes to reworking perfectly good data. In my original post concerning World Port Index Data, I failed to notice that large portions of the southern hemisphere were misplotted. It turns out that a negative longitude should have read positive. In other words I had the East in the West.

Now is a good time for me to remind all of you, use this data at your own risk. I do the best that I can with the data, software and expertise I have. Almost all of the time, I do excellent work. Sometimes, though, I do misplot data.

The WPI data comes from NGA data, Pub-150. Initially, I had extracted the data from MS Access into MS Excel, loaded the file and reworked it so it could be plotted. Unfortunately, I messed up on data in the southern hemisphere.

I have reworked the misplotted points and have them positioned correctly. I understand if you are leery about the quality of this data, but I am almost certain that all of the misplots have been corrected. Regardless, the World Port Index data is available, in SHP format, for download at this link. Good luck with it. If you find problems with the data, let me know and I will correct them ASAP.

Enjoy!

How To Turn a Black Sea Transparent

Nisos Skiathos - LIIM with a Black Sea (1:90,000)

Let's begin with the LIIM of Nisos Skiathos. There are times I would like to switch off a range of colors or, for that matter, switch off any colors I wish to. I asked Mike at Global Mapper if a modification like this would be possible. He said that it seemed to be a fairly simple process and he would modify Global Mapper v9.0 to allow this color by color control.

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How To Create Transparent Seas

The process to switch a color or multiple colors off is simple. The image I used is a GeoTIFF 8-bit. Within the Overlay Control Center select the image and open it with Options. Select the Transparent feature and you will be given a palette of colors. This image contains 255 colors using the GeoTIFF 8-bit image option. Either use the shift-key to select a range of colors or the control-key and pick and choose any colors you want. I selected all of the colors that defined the black sea. Switching them off gave me the image below.

Nisos Skiathos GeoTIFF 8-Bit Transparent Sea (1:90,000)

Pretty slick, huh? The process to switch off the black sea and make it transparent took about 30-minutes to complete. I really like this feature. It allows for some pretty creative imagery analysis. For example, the burned area on Nisos Skiathos could be easy to isolate and study in greater detail.

Global Mapper's way of doing business - 1) Ask for a feature. 2) If it can be done, Mike will add the feature. If not, Mike will tell you straight up. 3) And the cost for the feature update - $0.

Enjoy!

Nisos Skiathos GR - And Another Sporades Island

Nisos Skiathos - LIIM from N-34-35_2000 (1:70,000)

Nisos Skiathos is the westernmost island of the Sporades. It is reported to be heavily forested with pine trees. However the ugly red splotch in the center of the LIIM is a burn signature. When a forest fire occurs on a small island, it puts all of the inhabitants at risk. This fire was restricted to the mountainous interior. It would have occured over 7+ years ago and I am confident organic ground cover has returned to the area. According to a Nisos Skiathos web site, the island is heavily populated with tourists during the summer months. They visit the old fortress at Kastro (NE), long stretches of sandy beaches and enjoy a festive nightlife in Skiathos town.

My perfect visit to this island would be off-season. I would spend my time exploring and visiting with the local folks. In the evening I would walk in the town looking at the shops and selecting a taverna to dine in. Then I would retire to my room overlooking the sea. I would relax on my balcony with a good book, a glass of 20-year old port wine, a Cuban cigar and soft music in the background. I would fall asleep at 1:00 AM, wake up at 5:30 AM and start all over again. Wow! Now that is living on the edge.

Nisos Skiathos - EVS Precision Marplot Map (1:70,000)

The map was created in approximately 4-hours. It was a fairly straight forward island mapping project. Nothing out of the ordinary. I am working on color schemes for my various map layers. The colors are still being explored. I have been using Marplot's text feature. One has the option of using five different fonts. You control the size of the text by selecting and dragging it until you are satisfied with the size. I have used Time New Roman font for this island mapping project.

Enjoy!

Nisos Skopelos GR - Another Island In The Sporades

Nisos Skopelos - LIIM From N-34-35_2000 (1:100,000)

Nisos Skopelos is a fertile and densely-wooded island. Adjacent to the town of Skopelos is a harbor that handles the ferry boat traffic - tourists and goods from the mainland. There are a few smaller harbors that provide safe haven for the sailing crowd, especially the harbor at Ormos Glossa.

Nisos Skopelos - EVS Precision Map with Roads (1:100,000)

This island project took about 6-hours to complete. The shoreline was completed quickly. The feature that took the greatest amount of time was the island's intricate road network. I used a map found on Skopelos Web Site. I georeferenced the map and placed it on top of my base image. I then carefully digitized the road network, paying special attention to the size classification of the roads. I imported the completed files into Marplot where I finished this map. The names and locations of various island features were taken from Sailing Directions Pub 132, Section 16-10.

I have secured approval to use the road network on this map from the copyright owner, Yiannis Chatzitrakosas. Landsat ETM+ does a poor job of showing roads and trails, where as Yiannis' map shows all class of roads on the island..

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 - Approaching 35,000 Page-Views and Counting

Approaching 35,000 Page-Views

Thanks!

Kyra Panagia GR - Home of a Monk-less Monastery

Kyra Panagia - LIIM From Landsat N-35-35_2000

A few nights ago I decided to make a map from one of my Greek and Turkish Island LIIMs. I selected one at random. I initially had it identified as Nisos Pelagos. It turns out that the Greeks named the island after a monastery located on this island.

Kyra Panagia - EVS Percision Marplot Map (1:50,000)

The map I produced is above. EVS precision is the best resolution freely available. So I used the LIIM to create my map. Nothing much out of the ordinary to report. The map was created in less than four hours. What I found out about the island in the research phase, now that is interesting.

Kyra Panagia Monastery (Overview)

This humble monastery is monk-less. The last monk died in 1991. Tourist haul into Monastery Bay, climb Monks Steps and tour the only building on the island - this monastery. It turns out the island is uninhabited. It is a protected area - some sort of National Park status. So, if you are hunting for the ultimate get-away, this is your destination.

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!

Isla Pinta EC - Will Lonesome George Find a Mate?

Isla Pinta - Landsat N-15-00_2000 (1:90,000)

Isla Pinta - EVS Precision Marplot (1:90,000)

This project took about 4-hours to digitize. The shoreline is a composite of two images. The majority of the shoreline was taken from Landsat ETM+ imagery. When it is cloud free, this imagery is easy to work with. However, when you have cloud obscured shorelines, they are often impossible to discern. The second image used is DigitalGlobe imagery taken from Google Earth. This allowed me to digitize the eastern shore.

I have included four additional layers of information, besides the shoreline - a Vegetation Sparse layer, Land Bare, Land Lava and Land Rocky Shore. All of these layers were taken from the Landsat ETM+ image.

Isla Pinta - DigitalGlobe Image from Google Earth - Eastern Shore (Red Polyline)

I love DigitalGlobe imagery! It is the best to work with, but there are so many real and possible restrictions that apply to derivitive works, maps in particular, that it is more trouble than it is worth. The red polyline is what I digitized from the DG image. I imported it into Global Mapper and stitched it into my EVS precision shoreline.

Isla Pinta - EVS Precision Marplot with 50-meter Contours (1:90,000)

Isla Pinta - EVS Precision Marplot with 50-meter Contours 3D View (1:90,000)

I took my completed map image and georectified it on top of my Global Mapper data. I also added the SRTM data to create contours and explore 3D views of the island. The first map above has 50-meter contours. The second image is a 3D view of the island looking toward the NE.

Lonesome George at the Charles Darwin Research Station (Credit: Credit: Alison Llerena/CDRS)

And finally, here is Lonesome George. He is the last Pinta Island tortise. He was found in 1972 and removed to Santa Cruz Island. He has a couple of Wolf Island female tortises as his potential mates. So far Lonesome George continues to play hard to get. He is estimated to be between 80 to 90 years old. If he doesn't hook up with a female tortise soon his Pinta Island breed ends. I wish him well and his future mate many tortise children.

Enjoy!

Data - 78 Tuamotu Atoll LIIMs and They Look Great.

Tuamotu Atoll LIIMs

List of Tuamotu Atoll LIIMs

What is a LIIM? It is an island image extracted from Landsat ETM+ imagery - Landsat Island Image Mosaic - LIIM. I have just completed LIIMs for the Tuamotu Atolls. These low-lying atolls are northeast of Tahiti and southwest of the Marquesas. I have created a total of 78 LIIMs - one for each atoll. They range in size (MBs) from Rangiroa Atoll at 28.7MBs to some of the small atolls under 1MB. As I did with the Greek and Turkish islands, each zipped file contains a JPG image and two georectifying files, they are 14.5 meters per pixel resolution and 300 DPI. I did not save them with DEM files as most of them are very low lying islands. All files are UTM projection with WGS-84 datum. A handful of the LIIMs have cloud-obscured areas, but overall the images are quite clear.

Before DigitalGlobe imagery in Google Earth, I did all of my island mapping with Landsat imagery. I would love to continue using DigitalGlobe imagery, but I feel the copyright restrictions are too cumbersome to deal with. Using Landsat imagery, one can map to their heart's content. One could even make money off of their mapping. Wouldn't that be a kick?

The same offer I made with my Greek and Turkish LIIMs applies to the Tuamotu Atoll LIIMs - drop me a line if you would like to try one of these out. I will email a link where you can download the appropriate LIIM. All I ask is that you give me some feedback as to their usefulness and ease of use. So, if you would like to try one of the Tuamotu Atoll LIIMs, drop me a line.

Enjoy!