Thoughts - I Wonder If They Have Layoffs at North Sentinel Island?

North Sentinel Island - EVS Map (1:62,500)

During this difficult economic time throughtout the industrialized world, I am curious if more remote regions are escaping the more dire consequences - the layoff from your job. Friends and family are undergoing this economic rite - to be told you are no longer needed in your economic contributions. Those contributions generate an income that you and your family require, but your employer does not. What a mess!

Do you think the Sentinelese of North Sentinel Island have layoffs? I suspect that as long as they are able to contribute to the good of the group, typically 30 to 50 individuals, they remain as members. They are allowed to gather food and game to sustain the life of the group. No need for flat screen TVs, no electricity. Homes are simple shelters that provide protection for a family. They might banish a law breaker for acts harmful to the group and justifiably. But because times are difficult they would not abandon a member of their group. No they would find ways to solve their problem by productively employing all members of their group, not by selectively removing members.

Where did we go wrong? Why does civilization, industrialized civilization, marginalize members through their removal from economic contributions?

I am just rambling. Sorry for the rant, but it has been a rough week for my family and there are times that the life of a Sentinelese looks very attractive.

Take care, friends.

Taongi Atoll - Uninhabited, H-Bombs and My EVS Precision Map

ARB-127 Ornithology of the Marshall and Gilbert Islands

Taongi Atoll (H.O. 6024) ARB-127

Marshall and Gilbert Islands ARB-127

I enjoy reading the Smithsonian Atoll Research Bulletin available at the above link as PDF documents. First encountering them at Scripps Institute of Oceanography's library, I most especially enjoyed the detailed discussion of specific atolls. The articles are scholarly in content, yet accessible to the interested public.

A few years ago I took a class on how to work with enamel. It was instant gratification. Coat the copper plate with different colors of enamel, cook for about 1-minute at 1500°, let cool for 5-minutes and you have your finished work of art. You'll never guess what I made, my very first project was a map of an atoll, Taongi Atoll. I used the ARB-127 map based on chart H.O. 6024. It turned out nice. Why Taongi, why not!

Last week I was browsing my collection of ARB's and was looking at the collection of maps of all of the Marshall and Gilbert Islands which make up a significant portion of ARB-127. I studied the Taongi Atoll map and decided that I would make an EVS precision map of the island. Using Landsat N-59-10_2000 as my base image I constructed my map in about 4-hours. The bulk of the time was spent digitizing the coral heads scattered throughout the lagoon. But more on that later.

Operation Hardtack - Proposal to include Taongi Atoll as H-bomb test site

While researching the atoll, I came across a once classified document proposing that Taongi Atoll be used as a site to explode atomic bombs. This atoll would have been the third atoll besides Bikini and Enewetak, to be catastrophically damaged by slowly desolving nuclear radiation. Cooler heads prevailed and Taongi Atoll was spared. The ordinances intended for Taongi Atoll were exploded at the Nevada test site.

Taongi Atoll - Landsat Image from N-59-10_2000 Standard Landsat ETM+ Colors (1:110,000)

Taongi Atoll - Landsat Image from N-59-10_2000 Modified Colors for Reef Digitizing (1:110,000)

Now for my map. I was convinced I could create a map that would be far superior to the H.O. 6034 version in ARB-127. Looking at the standard Landsat image, I could see that the mapping would be uncomplicated. Curious soul that I am, I decided to play around with colors. After a number of color tweaks, I discovered the puke green image. The shallow reef was a lighter puke green and the deep reef a different shade of green. As a bonus this color tweak turned the island vegetation into a reddish pink. In addition, this color scheme allowed for a greater number of coral head to be digitized.

Taongi Atoll - EVS Precision Map (1:110,000)

And here is my finished map. The scale is 1:110,000 (1 cm = 1.1 km). My finished EVS precision map of Taongi Atoll contain my normal vector layers; island polygon, vegetation, shallow reef and deep reef. I tried something different when labeling. I used a feature in Global Mapper to assign text to a specific point and in this way I assigned lat/lons. The island names and other text were also assigned using Global Mapper. I used MS Draw to construct the lat/lon lines. I think this is a good mapping effort.

Today, the atoll is a nature preserve and remains uninhabited. Thanks to some unknown beaurecrat, the island remains nuclear radiation free!

Enjoy!

Thoughts - Rapa Iti's Hydrographic Layer

Rapa Iti Island - Ikonos Image (1-55,000)

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Rapa Iti Island - Other Precision Map (Ikonos Image) Hydrography Layer (1-55,000)

I believe Rapa Iti's hydrographic layer is almost complete. I always QC my digitizing before I determine a layer finished. I am watching the Pacific Life Holiday Bowl (score Okla St 31 and Oregon 42) and composing this post. A few moment ago my mother-in-law asked what my map showed. I explained that I had mapped all of the places where water would flow during a rain storm. She thought that was interesting, but liked the colors best.

The QC of this layer will involve a final classification of the streams. They will be classified as permanent streams identified by vegetation, stream width and visible water. Any or all of these characteristics evident will cause me to classify the stream as permanent. All other streams will be classified as intermittent streams.

This system of classification will have to do short of me visiting the island for a month during the rainy season and spending the time hiking to various points about the island to study water flow. Oh well, one can dream.

Enjoy! And Happy New Year!

Thoughts - Digitizing Rapa Island's Hydrography Layer

Rapa Island, North Shore - Ikonos Image with Digitized Hydrography Layer (1:1,250)

Rapa Island, North Shore - Other Precision (Ikonos) Map with Digitized Hydrography Layer (1:1,250)

Sure, I've been busy with family, friends and 12 dozen tamales served all day Christmas day at my home. Come Christmas evening I was still entertaining guests and wishing I could continue working on my current mapping project, Rapa Island. I have mapped this island a number of times, each time not completely satisfied with the finished project. So I've decided to work on this island one more time. First I redigitized the shoreline working at scales between 1:1,250 to 1:850 using a hi-res Ikonos image. After completing the shoreline, I decided to work on the island's hydrographic layer. Initially I've classified each valley as a potential stream course. The island has a number of permanent streams fed by frequent rain storms and springs. Most of the streams I've currently mapped will be reclassified as intermittent.

Rapa Island - Other Precision (Ikonos) Map with Hydrography Layer (1:52,500)

I've mapped most of the hydrographic layer over the last 5-days, actually over the last 5-evenings. The hydrography of the western portion of the island remains to be digitized. I hope to have the layer completed within the next few days. When it is finished, I intend to digitize the vegetation layer next. I'll keep you informed as to my progress.

Enjoy! Merry Christmas and Happy New Year!

Coronado Islands MX - For The Birds and Fishermen

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Coronado Islands - Spot Image from Google Earth (1-35,000)

Coronado Islands - Other Precision Map Using Spot Image From Google Earth (1:35,000)

Located about 25 kilometers south of the entrance to San Diego bay, these Mexican islands are often mistaken as US possessions. Most San Diegans know of these islands and a few of the stories associated with them. For instance, we know that there was a gambling establishment on South Island that was a going concern well into the Depression. We know that the islands were used as a haven for Prohibition smugglers. Today there is a small Mexican military detachment stationed on South Island to keep an eye out for human smugglers and fishing poachers. The islands are visited daily by fishermen, divers and numerous sea birds, especially brown pelicans.

I first saw the islands as a young boy back in 1954. From that perspective they appeared to be two buffaloes. To others they look like coffins. To me they are always a welcome site.

The map was constructed from an image mosaic I created using the Spot image found in Google Earth. From this georeferenced mosaic I was able to work at a scale of 1:5,000. As a result, the shoreline details are excellent. I tried using SRTM 30-meter to generate contours and the results were not satisfactory. I knew of a series of geologic maps of the islands containing 20-meter contours on a San Diego Geology website. I georeferenced the contour containing images and copied the 20-meter contour intervals. When necessary, the contours were adjusted to align with the underlying Spot image.

Because my digitizing work was done at a scale of 1:5,000, the zoom factor for these islands gives one excellent details. I would suggest using Google Earth imagery to take a detailed tour of the islands. To enjoy an excellent map of the islands, this is the place.

Enjoy!

Thoughts - Generating Reliable Contours from SRTM Data

Isla la Plata - Other Precision Map (1-20,000)

Here is a comment and question concerning my use of SRTM data...

I am working on a similar project, in some aspects, about generating contours, and was wondering when the contours do not line up with your coastline (having 25 m intersect the shoreline of your polygon) do you alter the polygon or the raster data before generating the contours? Anyways, I think you work is beautiful, keep it up.

Here is my response...

Thank you for your kind words. I love making maps of islands and to be able to add meaningful contours is a great benefit. However, my experience with the SRTM 30-meter and 90-meter data is as follows. After loading both a georectified image and an SRTM file into Global Mapper, I am able to quickly generate contours at an interval I deem appropriate for the scale I am working with. In nearly every instance the lower level contours do not conform to the actual imaged shorelines. I end up manually realigning the contours to best match the imaged shoreline. As a result my lower level contours are reasonable, but suspect.

When I am dealing with a very large void that cannot be handled by combining SRTM 30-meter with SRTM 90-meter data or be filled with existing void-filling software (I use SRTMFill), I end up guesstimating alignments of contours. Consequently, all of my maps containing contours are as good as the underlying SRTM data - sometimes excellent (upper elevations of Isla la Plata map) and less reliable (10-meter to 30-meter contours and northern contours due to a void).

I am not practiced enough to correct the underlying SRTM ASCII data, so I rely upon working with software (SRTMFill), imagery to contour reconciliation, or when cloud-obscured, an educated guess using secondary imagery.

Hopefully, this answers your questions. Perhaps you have techniques or know of SRTM void-filling software that might correct many of my issues concerning misaligned or voided elevation data. I do believe that SRTM 30-meter and Landsat ETM+ at 14.5-meter resolution can work reasonably well together. However, combining SRTM 30-meter with 1-meter resolution imagery most often creates many slight, but consistent contour misalignments.

SRTM elevation data, as stated above, gives us a reasonable idea of the topography of the underlying land. I would use it to go hiking, but I sure would not bid a construction job based on it.

Enjoy!

Isla la Plata - Ecuador's Bird Island

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Isla la Plata - Landsat Image S-17-00_2000 (1:20,000)

Isla la Plata - DigitalGlobe Island Mosaic from Google Earth (1:20,000)

A group that removes feral animals from islands asked if I could help them with a map of Isla la Plata located off the coast of Ecuador. I said sure and began to search for a map or image of the island. The only map was something that was painted on a sign posted on this island. Not very accurate, but colorful. I tried the Landsat ETM+ image and found it to be obscured by clouds at a number of points on the island. I finally looked into Google Earth and found the DigitalGlobe image that covers the island. Except for clouds over the northern tip of the island, the image is exquisite. To create the above mosaic which is 12.4MBs and 4500 x 4120 lines, I copied 24 images (1280 x 911) and pieced them together. This image was georectified using Global Mapper, Landsat ETM+ and Google Earth coordinates.

Isla la Plata - Other Precision Map (1-20,000)

This is the resulting map. The parties wanting to use the map did not require a vegetation layer so all that I had to map was the island shoreline. That took about 4-hours to map, not just the shoreline, but all of the offshore rocks as well. Finally, using SRTM 90-meter and 30-meter data, I generated 10-meter contour intervals. As so often happens, the 10-meter to 30-meter contours ended up in the ocean. I spent another 4-hours adjusting contours so that they resided on the island and not in the deep blue sea.

This map is done. I hope the party using it will find it helpful. I reminded them that they could not publish this map without permission from DigitalGlobe. It is my experience that DigitalGlobe is very open to allowing maps derived from their data to be used for educational research and perhaps for the removal of feral animals from fragile islands.

Enjoy!