Thoughts - Bigger is Good, Smaller is Better

View Larger Map

Nisos Aegina - Landsat Island Image Mosaic N-34-35_2000 (1-125,000)

I am currently reworking my map of Nisos Aegina. It is a bedroom island outside of Athens, Greece. A nice little getaway when life becomes too hectic in the big city. But this isn't the reason for this post.

You know that I construct island maps using Landsat ETM+ mosaics as my base imagery. I have a Landsat ETM+ digital library of all of the world's shorelines. I use Global Mapper software to digitize, creating vectors from which i construct my island maps. This software handles the Landsat ETM+ mosaics with ease. I have invested over $500 in Global Mapper and do not regret a cent of it. The software does exactly what I want it to do and Mike, the boss and software guru, keeps making improvements. But this isn't the reason for this post either.

This post poses the age-old question "Is Bigger Better?" as it applies to the world of imagery.

In the world of Landsat derived island specific orthorectified imagery, bigger is not necessarily better. This is the world of imagery anywhere from multi-GB files to a few hundred MB files. These very large image files test the limits of most software packages. Often their formats, (i.e., MrSID) require special handling to open and work with. Since I primarily work with island imagery, I figured that if I were to cut out the ocean and save the island and it's surrounding reefs at a scale allowing me to work at increasing zoom ranges, I could create the same high quality maps from much smaller sized imagery.

First I fashioned a series of Greek island mosaics (see above image). These were followed by a series of Tuamotu Atoll images. I call my creations Landsat Island Image Mosaics (LIIM). Here are a couple of examples showing the zoom capabilities using the Nisos Aegina LIIM as base imagery.

NIsos Aegina - Detail Western Shore LIIM N-34-35_2000 (1-25,000)

Nisos Aegina - Detail Aegina Harbor LIIM N-34-35_2000 (1-12,500)

I typically digitize shorelines and certain land use features at scales between 1:25,000 to 1:12,500. I know that this pushes far beyond the intended limits of Landsat-7, 14.5 meter resolution imagery. I have digitized at these limits for over four years. The resulting maps have a level of quality and precision that exceeds most widely available island mapping. My island maps have been used by a number of universities to further research and as a platform for spatial analysis by insurance companies.

The size advantage with these considerably smaller island images is significant. My LIIMs range in size from 2 MBs up to 45 MBs for very large islands. All of my LIIMs are saved as georectified JPGs. Nisos Aegina LIIM is 3.47 MBs and is a 15.8 MB Tif file. The Landsat image containing this LIIM, on the other hand, is 106 MBs. The image degradation is slight and barely noticeable. So, I will keep using my LIIM of a specific island from which to create my island maps. If you would like to use one of my LIIMs, drop me a line. I'll fix you up.

Enjoy!

Comparison - 14.5-meter vs 1-meter and Monoplotted Shorelines

Landsat ETM+ and DigitalGlobe from Google Earth (1:18,000)

I have heard from many readers that maps derived from 14.5-meter resolution are useable between 1:125,000 to 1:62,500. To push them down to scales below 1:62,500 would render the map virtually useless.

Palmerston Atoll - Bird Islands (1:15,000)

That was before I discovered a LINZ produced map of Palmerston Atoll at a scale of 1:25,000. My EVS precision shoreline was a very close approximation of the LINZ product. It was so similar that it was as if LINZ might have used the 14.5-meter resolution imagery to produce their island map. I asked them and never got a satisfactory answer. My guess is that they did make use of the 14.5-meter imagery to produce their 1:25,000 scale map. Just a guess, but a good one.

EVS Precision and EEVS Precision Shorelines with Reefs (1:18,000)

Using the first image in Global Mapper, I digitized both shorelines at 14.5-meter resolution and 1-meter resolution. The left map (less vegetation layers) was created from 14.5-meter imagery. The map on the right was created from 1-meter imagery. I am certain DigitalGlobe's 1-meter imagery is the best hi-res imagery currently available, thanks to Google Earth. I confidently acknowledge that shorelines, reefs, vegetations layers and other layers of information derived from 14.5-meter resolution imagery is good mapping information. As with any imagery, one needs to make mapping compromises. Perfection at tracing a dynamically shifting shoreline is impossible. Tha shoreline's ultimate delineation can be approximated, at best. My EVS precision work allows me to create and use mapping products at scales far below 1:62,500 - like 1:25,000.

Enjoy!

Bikini Atoll RM - Great Dive Destination If You Don't Mind The Glow

Bikini Atoll - LIIM N-58-10 (1:200,000)

I decided to digitize this atoll because the Landsat Island Image Mosaic is cloud-free and it has a certain amount of notiriety connected with nuclear weapons testing and population displacement. As a youngster, I watched rebroadcasts of one of the blasts on TV. It was probably the Bravo blast, the one that left the big hole in the northwest portion of the reef.

The islanders are still displaced. It seems they tried to reestablish themselves back in the 70's. After awhile they were beginning to glow (figuratively speaking). They were taken off of their home and scattered onto other islands. Now, tourists are allowed to visit, along with divers and fishermen. The island and it's waters have been deemed safe for short stays. Just don't drink the groundwater, eat the coconuts, land crabs or fish. One advantage if you stay for a long time - you won't need a lantern at night, your radioactive glow will provide sufficient illumination. Just a joke. I know that folks earning their livelihood from tourists, divers and fishermen will resent my "glow" remarks. I apologize to them. But, the U.S. military screwed up when they blasted holes in this atoll. 60-years later, I still say, "Shame on you."

Bikini Atoll - EVS Precision Map (1:200,000)

Enough about my personal gripes. The EVS precision map of Bikini Atoll was a fairly fast project to complete. The digitizing took 8-hours over a period of 2 days. The map assembly and posting has taken another 2-hours. 10-hours from start to finish for an island of this size is good. The reef, thank goodness, was relatively simple to digitize. Some reefs are quite complex and require many layers of information. This reef consists primarily of three layers - EVS Reef Shallow, EVS Reef Middle and EVS Reef Deep. They are distinguished by their respective shades of blue. The majority of the lagoon is classified as EVS Reef Deep. I used only a single vegetation layer, EVS Vegetation Mixed (Hi-Lo). I use this classification on most Landsat imaged islands with a mixture of palms and other trees along with shrubs and low-lying plants. When I am able to study a DigitalGlobe hi-res image along with the Landsat, I am able to make better vegetation layer classifications.

I still have work remaining on this project - EVS Reef Awash where visible waves appear along the outer reef and confirmation of individual motu names When I am satisfied with the outcome, I will repost the map. Until then...

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.

<

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!

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!

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!

Thoughts - Landsat Island Image Mosaic

I have over 600+ Landsat ETM+ Orthorectified Mosaics that two summers ago I patiently downloaded and copied onto a series of DVDs. These mosaics cover all of the shorelines and oceanic islands throughout the world. It is an impressive collection. This collection, coupled with Global Mapper v9.01 (GM), allows me to load and view the individual mosaics as I desire. Each mosaic, even compressed in MrSID format, is typically 100 to 250MBs. Them is some big files!

Over a year ago I had a discussion with a reader who wished to work with these files to make his own maps. I described where he could download the files. But, alas, he said the files, even in MrSID format, were too large for his system. Was there a smaller file of just individual islands, he asked. Not to my knowledge, I guessed and went back to making maps of islands.

That was until this past month and my work in image mosaics. First I worked with DigitalGlobe imagery. Sadly, they have never responded to my product idea. Oh, well, so goes life. Lately, I've been working with Landsat ETM+ again. And the following is my latest idea - Landsat Island Image Mosaic or LIIM.

Greek and Turkish Islands - Landsat ETM+ Mosaics

Some of my earliest mapping efforts were of Greek and Turkish islands located in the Aegean Sea. This area is virtually cloud-free and the clarity is outstanding. However, it takes seven Landsat mosaics to cover the area. Using a raster export feature within GM, I experimented with various raster formats and came up with georeferenced JPG. Pixel size of each resulting LIIM is 14.5-meters, 300 DPIs and projection is Mercator. The resulting image is outstanding.

Nisos Limnos - Landsat ETM+ N-35-35_2000

I zoomed into my target area encompassing the primary island and created the georectified JPG. The above Nisos Limnos LIIM taken from GM gives the user the complete resolution power of Landsat ETM+ without the size problems. The above file, along with it's accompanying DEM, is only 7.2MBs.

Greek and Turkish Islands - SRTM Tiles

To really bring the Nisos Limnos LIIM to life, the SRTM data is the ticket. To cover the Aegean Sea one needs 83 individual SRTM tiles. Loads of data for most of us. Many of these tiles require some fixing, which is done using SRTM Fill (freeware) to fill holes. Once this data is loaded, GM allows for DEM creation. One is able to take the Nisos Limnos DEM and drape the Nisos Limnos LIIM on top and get a variety of 3D views of the island.

Nisos Limnos - SRTM N039E025

So I exported the underlying area into DEM format. This allows for some nifty looks at the island

Nisos Limnos - 3D View

Pretty cool! This is the Nisos Limnos LIIM draped over the Nisos Limnos DEM. All of this wrapped up in a 7.2MB package. I like it. How about you?

I should add that I have created 16 Greek and Turkish Island LIIMs. The following islands have LIIMs - Bozcaada, Gokceada, Nisida Fournoi, Nisida Gioura, Nisos Agios Efstratios, Nisos Alonnisos, Nisos Chios, Nisos Ikaria, Nisos Lesbos, Nisos Limnos, Nisos Pelagos, Nisos Samothraki, Nisos Skiathos, Nisos Skopetos, Nisos Skyros and Nisos Thasos. I intend to complete coverage of the islands of the Aegean before I head back to school on Jan 03, 2008.

Enjoy!