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!

Yadua Taba Island FJ - Home of the Fijian Crested Iguana Project

Yadua Taba Island - Landsat S-60-15_2000 (1:12,500)

Yadua Taba Island - EVS Precision Map (1:12,500)

As I was mapping this island, I kept repeating the Fred Flintstone saying "Yaba Daba Do". That was what Yadua Taba did to me. Now what it does for iguanas is something else. Yadua Taba is home sweet home to the few remaining Fijian Crested Iguanas. It is the hope of the Fijian Crested Iguana Project to enable the few remaining iguanas to survive. Not just survive, but perhaps to thrive.

Fijian Crested Iguana (from Reuters)

"A Fijian Crested Iguana sits on the head of a statue of a Komodo Dragon at Taronga Zoo in Sydney during an announcement of a funding boost for their conservation June 19, 2008. Only a few wild populations remain of the endangered iguana which is found on a several Fijian islands. The species faces possible extinction due to habitat destruction and competition from introduced species."

Enjoy!

How To Digitize Cloud-Obscured Shorelines

Raivava'e Atoll - EVS Precision Map on Landsat S-06-20_2000 (1-55,000)

As most of my regular readers know, the bulk of my mapping work is derived from Landsat ETM+. My primary reason for using Landsat ETM+ as base imagery is consistency of product. Typically, anywhere on earth this imagery is freely available, virtually cloud-free and consistently resolved to 14.5-meters per pixel. Great for my worldwide island mapping work. Plus, there are minimal copyright issues when using this imagery. All that is asked is that you credit the source imagery. Did I say "virtually cloud-free"? That is everywhere but in humid climates, in other words in and around islands. Oh, well, it is merely a challenge that the accomplished mapper learns to work around.

The above image is an example of cloud-obscured island imagery. Most of Raivava'e Atoll is visible, but those areas not visible are significant. How does one resolve these areas using copyright-free data (credit source data)? If I am unable to secure Landsat 1990 imagery, which quite often enables one to resolve cloud-obscured areas, I go to Shuttle photography. Specifically, searching for ISS (International Space Station) imagery.

Raivava'e Atoll - EVS Precision Map on ISD_ISS001-375-13 Modified (1-55,000)

Raivava'e Atoll has two images that show the atoll with virtually no clouds. These images are sufficiently large enough that one is able to zoom into and digitize features. First, however, the ISS image must be georectified. Global Mapper allows me to georectify ISS imagery using my Landsat base imagery. In georectifying this ISS image, I used 7 GCP's to ensure the ISS image lay precisely on top of the Landsat base image.

Raivava'e Atoll Outlying Motus - EVS Precision Map on Landsat S-06-20_2000 (1-10,000)

Raivava'e Atoll Outlying Motus - EVS Precision Map on ISD_ISS001-375-13 Modified (1-10,000)

Beginning with the cloud-obscured Landsat image above, I digitized as much of the atoll as possible. The cloud-obscured portions were identified and designated for further work. Visiting Shuttle photography, I found 2 cloud-free images of Raivava'e Atoll. I selected ISD_ISS001-375-13 as the better of the two images. I rotated it and cropped to the atoll. Using this modified ISS image, I was able to complete digitizing the cloud-obscured shoreline. When all else fails, I use WVS shorelines. They are crude compared to EVS precision, but they work.

I use red shorelines to designate EVS precision derived from Landsat base imagery. The green shorelines are designated as Other precision. The source for all Other precision shorelines in my Raivava'e Atoll map is the ISS imagery.

My EVS precision island map of Raivava'e Atoll is complete and I was able to digitize all shorelines in spite of clouds. Pretty cool, huh?

Enjoy!

Espiritu Santo NH - EVS Precision Details

Espiritu Santo NH - EVS Precision Map

A simple slideshow is all you get with this post. A simple slideshow of a detailed map of Espiritu Santo island. What I intended to demonstrate with this post is how detailed a shoreline one can create at EVS precision. Mapping created from 1-meter resolution imagery is far superior to Landsat ETM+. However, nothing in the public sector rivals EVS precision. Not WVS, Not NGA PGS, Not DCW. No non-commercial shoreline mapping rivals it. Not many commercial shorelines mapping rival it either. The nice thing about mapping at EVS precision, once it is finished there is no reason to redo. It is finished. And tonight, so am I.

Enjoy!

North Sentinel Island IN - Still The Most Isolated People

North Sentinel Island - Landsat ETM+ Image Circa 2000 From Google Earth (1:62,500)

North Sentinel Island - ESA Image 2005 (1-62,500)

Let's begin this post with a discussion of my two base images. The first one is a modified Landsat ETM+ extracted from Google Earth. I have the Landsat ETM+ image found on N-46-10_2000 and used it for one of the vegetation layers found on my completed map. However the shoreline, sand beach and forest was extracted from the Google Earth image. Both of the above images were georectified to my N-46-10_2000 image. The Landsat image is circa 2000. The ESA image was taken following the devastating December 2004 earthquake and tsunami. The offshore reefs underwater in the circa 2000 image are uplifted. They were raised as a direct result of the 9.0 earthquake. The island was also hit by a series of tsunamis which created death and destruction throughout the region.

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

My map displays both shorelines of North Sentinel Island. The enlarged beaches and submerged reefs are parts of the new shoreline. The island proper was mapped at scales between 1:12,500 to 1:6,250. The new shoreline and raised reefs were mapped at a scale of 1:50,000. The map is a nice effort. It looks good and reflects the effects of the December 2004 earthquake.

Sentineli Man ShootIng Arrow at Helicopter

I want to say a few things about a group of people that call North Sentinel Island home. They have called it home for about 60,000 years. They are a remnant of the original "out-of-Africa" movement around 100,000 years ago. Follow this link to the Andaman Association and their fascinating site about the Lonely Islands (Andaman Islands). George Weber has gathered information about the inhabitants of the Andamans and specifically the people inhabiting North Sentinel. This group wants nothing to do with the outside world. The population estimate is about 250 individuals. The picture, taken from the Andaman Association website shows the Sentineli's defiant attitude. After the December 2004 earthquake and tsunamis, the Indian government sent a group of concerned scientists to North Sentinel to check on the well-being of the inhabitants. The heli was greeted by the lone man attempting to shoot the big bothersome machine out of the sky. The Sentinelese are doing just fine and they could care less about the world and all of its mysteries. In fact the few crude attempts at contact are clumsy, at best, and insulting most often. I hope they are able to survive, if only to remind us of that different way in which we all once worked with nature and which is so different from our attempts to mold and control nature today.

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 - FLASH! 8,000 Pacific Islands Mapped at EVS Precision

EPIP - Pacific Islands Overview

The 8,000 islands located in the following island groups: Papua New Guinea, Solomon Islands, Vanuatu, Fiji, Cook Islands, Western Samoa, Tonga and portions of Kiribati were mapped at EVS precision. Using Landsat ETM+ ortorectified image mosaics, which typically resolve to 14.5 meters per pixel as base imagery, Mr Minton spent in excess of 240-hours over 31-days digitizing, correcting and finalizing island shorelines throughout this region of the Pacific. Mr Minton used a variety of strategies to resolve cloud-obscured shorelines. Those that ultimately could not be resolved were mapped using World Vector shorelines. This impressive effort is being fine tuned using 1990 Landsat imagery, when available.

You heard it right! I spent the last month mapping thousands of islands at EVS precision. I did get paid to do it. Part of me wants to rest, as I sure deserve it. However, the island mapper in me demands that I resolve problem areas, primarily cloud-obscured areas, by correcting island shorelines using cloud-free imagery.

If you are interested in these shorelines, email me and let's talk.

Finally, I will finish mapping the balance of the Pacific islands at EVS precision. Stay tuned for updates on this effort.

Enjoy!