Guadalupe Island MX

Thursday, December 28, 2006

Guadalupe Island MX

I have wanted to map this island for quite some time. Landsat imagery was full of clouds, not good to map details of both shoreline and the island proper. I located some ISS imagery that was relatively clear. The resolution was crude compared to Landsat. Finally Google Earth managed to snag some 1-meter resolution Digital Globe imagery. I had the perfect image, now I just needed time, like Christmas vacation. I have worked on this map and the various layers for about 10-hours. The shoreline is as good as it gets. The northern end of the island is cloud obscured and I had to use ISS imagery to approximate the shoreline. However, the bulk of the shoreline is crystal clear.

Mapping in Google Earth is a challenge. In Marplot it is easy to create multiple features within the same layer (i.e., five Cypress Tree Groves). In GE, each feature stands by itself. I had to create five separate files for each grove of trees. The problem comes when you have many features (i.e., small islets ringing this island). I had to create 13 separate KML packets. Each had to be handled separately to reformat so that they could drop into Marplot.

This island was ravaged by a variety of feral animals, goats and rabbits primarily. The goats eat anything and everything. They were eating the Cypress tree seedlings. They were destroying this unique ecosystem. The Mexican government and US agencies have worked cooperatively to eradicate these feral pests. I noticed that the large stands of Cypress trees are ringed by fences. Reportedly, the goats are almost completely gone. The fragile ecosystem is recovering.

Not in our lifetime, but in our children's children, they will be able to visit a verdant forest that will cover the entire higher elevation of this island. They will stay in a swank lodge and for fun take long hikes. No, not in our lifetime, but perhaps our children's children will experience it.


PS - The SRTM data was great, so I created 100-m interval contours. Now the map image contains the EVS Contours layer. And now I am finished with Guadalupe Island.

Labels: , , , , , , , , , ,

posted by Mr Minton at 1:29 PM 0 comments

Tatakoto Atoll FP

Wednesday, December 27, 2006

Tatakoto Atoll FP

Tatakoto (17˚20'S., 138˚25'W.) is a low atoll about 90 miles NW of Pukaruha that is wooded on the NW part. The lagoon is inaccessible from the sea, but a landing may be made near a flagstaff in a village on the atoll's W side.  (SD Pub-126)


Other names given by European discoverers: Augier, Narcisse

Tatakoto is located 1,182 kilometers (724 miles) from the island of Tahiti and some 180 kilometers (119 miles) from the nearest inhabited atolls of Vahitahi and Puka Puka; Tatakoto is undoubtedly one of the most remote atolls in the Tuamotu Archipelago as well as all of French Polynesia.


This bean-shaped atoll is 14 kilometers (8.7 miles) long and 3.5 kilometers (2.2 miles) wide. It is located at 17°20’ south latitude and 138°24’ west longitude.
Tatakoto covers an area of 730 hectares (1,804 acres) divided up into 65 islets, or motu. Its lagoon, which covers an area of 1,970 hectares (4,868 acres), is 11 kilometers (6.8 miles) long and 2.5 kilometers (1.6 miles) wide. The biggest motu is 15 kilometers (9.3 miles) long and 400 meters (1,312 ft.) wide, covering the entire north coast of the atoll in an east-west direction. The southern side of the atoll is exposed to prevailing winds and is composed of a series of motu separated by small passes. The biggest motu has an unpaved runway that is practical for flying out copra. The village of Tumukuru is concentrated on both sides of the main road and along the coconut plantation road, an overall area measuring 600 meters (1,969 ft.) long by 200 meters (656 ft.) wide. Six main streets crisscross the village of Tumukuru, which is located on the western point of the atoll. Tatakoto has an aerodrome located near the village, but the atoll does not have a pass through the coral reef enclosing the lagoon. The village has a whaleboat dock and a 25-meter (82-ft.) pier. A second whaleboat dock is located in the southern part of the atoll.


Two Spanish explorers—Domingo de Boenechea and Andiay Varela—sighted Tatakoto independently of each other on the same day in 1774, becoming the atoll’s first European discoverers. From 1900 to 1927 Frenchman Albert Javelot served as the atoll’s chief, planting the atoll with coconut trees that still cover the atoll today. The 1996 census recorded a population of 247 persons.

(From Presidency of French Polynesia Web Site)

Atolls are both satisfying and frustrating to map.  They take hours to complete.  This atoll consists of 13 identified layers and another 4 additional layers.  Each layer of information requires consistent identification and delineation.  Each atoll's EVS Reef Middle, for example, should be consistently identified from the Landsat mosaics used as base imagery no matter the island.  The steps to create a map such as this are both tedious and demanding.  Now for the good stuff - the finished map looks great!  It not only looks great, it is a solid cartographic effort.  Even before I began this project, I knew that ultimately the finished product would look great.  The base imagery is clean and provides a crisp picture of the atoll.  The challenge was to keep working.  And that is just what I did.


Labels: , , , , , , , , ,

posted by Mr Minton at 11:26 AM 1 comments

Swains Island AS

Swains Island - Image

Swains Island - Landsat Image S-02-10_2000 (1:25,000)

Swains Island - Map

Swains Island - Marplot Map (1:25,000)

The entry in Sailing Direction Pub-126 is merely to state the name of the island and it's location. The better information comes from Jane Resture's site and a US DOI site. So I won't rehash what they will tell you. The island sounds like a great place to visit, except for the flies and mosquitos.

The map was relatively fast to construct. It took about 3-hours from start to post. I did a change for the vegetation layer. I made it less "lime gree" and more of a "muted green". It is easier on the eyes.


Labels: , , , , , , ,

posted by Mr Minton at 11:24 AM 0 comments

McKean Atoll KR

McKean Atoll - Image

McKean Atoll - Landsat Image S-01-00_2000 (1:10,200)

McKean Atoll - Map

McKean Atoll - Marplot Map ()1:10,200)

McKean Island (3˚36'S., 174˚08'W.) is a treeless coral island, nearly 0.5 mile round in shape, set on a heart-shaped reef. Breakers extend about 0.3 mile from the N end and 0.2 mile from the S end of the island. The most conspicuous object on the island is the ruin of a large building on the W side, with a coral slab, 2.1m high. Scattered about are the ruins of several structures, obviously part of the old guano works. The island is a wildlife sanctuary.

Winds—Weather.—The winds are nearly always E, varying from NE to ESE, with the former predominating.

Tides—Currents.—The current sets strongly past the N and S points, converging on the W side of the island. Close in to the shore on the W side, the flood sets N and the ebb S. Offshore, the set is W with an average velocity of 0.5 knot, but varying in strength and direction with the prevailing wind. (SD Pub 126)

I mapped this island because of a reference to it in the Atoll Research Bulletin. This map took about 1 hour to complete and post. It's lagoon is classified as a EVS Wetland, because I don't have an appropriate layer designation yet for a lagoon of this nature. It is mostly full of salt tolerant vegetation and rubble. At high tide the lagoon has ocean water percolate into it. Atoll Research Bulletin 228 contain some interesting information about a brief scientific expedition to the island back in 1968. The information is still relevant.


Labels: , , , , , , , ,

posted by Mr Minton at 11:22 AM 0 comments

Birnie Atoll KR

Birnie Atoll - Image

Birnie Atoll - Landsat Image S-02-00_2000 (1:14,000)

Birnie Atoll - Map

Birnie Atoll - Marplot Map (1:14,000)

Birnie Island (3˚35'S., 171˚31'W.) lies about 43 miles S of the S extremity of Canton Island. The island is 3.6m high on the rim, sloping gradually to sea level at a shallow brackish pond located about 90m inland from the E side of the island. Birnie Island is a bird sanctuary.
A flat fringing reef, drying at LW and extending as far as 0.1 mile offshore, surrounds the island. A shoal, which breaks in heavy weather, extends 0.7 mile S from the S point of the island. A stone monument on the E side of the island, about midway of the length, is visible 6 miles and is a radar target for the same distance.

Tides—Currents.—Close into the W shore the current sets N. Farther off, the set is W and is usually at a rate of about 0.5 knot, with the strength and direction varying with the surface currents set up by the prevailing wind.

Anchorage.—Anchorage is possible about 0.3 mile off the NW point, in 16.5m, with E winds. The S spit is considered too dangerous for anchorage, as it drops off from a depth of 3.7m to 54.9m within 90m. (SD Pub-126)

This map was quickly constructed (2-hours). However I came up with two new layers - EVS Brackish Water (which describes brackish water lagoons that are fed through percolation of sea water) and EVS Uplifted Reef & Scrub Vegetation (which describes island surfaces that have tufts of vegetation and little sand). The image file was taken from Landsat ETM+. I got spoiled on my last island (Nikumaroro Atoll) working from Ikonos imagery. 1-meter imagery is sweet!


Labels: , , , , , , , ,

posted by Mr Minton at 11:20 AM 0 comments

Enderbury Atoll KR

Enderbury Atoll - Image

Enderbury Atoll - Landsat Image S-02-00_2000 (1:31,250)

Enderbury Atoll - Map

Enderbury Atoll - Marplot Map (1:31,250)

Enderbury Island (3˚08'S., 171˚05'W.) is a coral island consisting of a rim averaging 3.9m high, with a sunken central plain about 1.2m above sea level. The island is steep-to, with a very short reef which makes landing difficult because of the strong sweep of the undertow on the shelving shore. The shelf extends only about 68.5m and drops off rapidly except at the N and SE corners.

Winds—Weather.—The winds vary from the NE to SE. There are frequent, but usually brief rain squalls and they cannot be depended on as the sole water supply.

Tides—Currents.—Immediately W of the island, the current sets to the S with a strength of about 1 knot. In very strong flood tides this set may be reversed. Clear of the island, to the N or S, the average set is about 0.8 knot in a 255˚ direction.

Aspect.—A mast, marked by red obstruction lights, exists about 0.8 mile S of the N extremity. The most conspicuous objects on the island are several palms at the N end; a large guano heap, about 6.1m high on the W side; and the buildings of the settlement at the S part of the island.

Anchorage.—During the season of the Southeast Trades, there is opportunity to anchor on the spit off the NE point, in depths of 45 to 55m, coral and sand. The anchorage should be approached slowly from the WNW with constant use of the depth sounder, as the spit is very narrow and may be overrun easily. The observed set of the current at this anchorage is to the NW, which keeps the stern away from the shore. Anchorage here is not recommended when the Northeast Trades are blowing.

Directions.—The landing place is on the W side of the island, just N of the settlement. Ships may approach the island to within less than 0.8 mile at this point. Landing may be affected by a surfboat through a channel in the reef leading in on a range of two beacons, in line bearing 092˚. Great care must be used in landing as the reef is short and steep, and the channel is narrow with rapid shoaling toward the landing. The best landing conditions prevail at HW and with a strong E wind, which flattens the swell that usually sets in from the S. (SD Pub-126)

This project was relatively fast (2-hours). I am having fun working on these little islands. They are relatively uncomplicated. Most of them are Bird Sanctuaries and are Protected Areas that require approval before you can land. People tried to mine a low-grade of guano for a few years. Now the island is home to birds and feral cats.


Labels: , , , , , , , ,

posted by Mr Minton at 11:17 AM 0 comments

Rawaki Atoll KR

Rawaki Atoll - Image

Rawaki Atoll - Landsat Image S-02-00_2000 (1:12,500)

Rawaki Atoll - Map

Rawaki Atoll - Marplot Map (1:12,500)

Rawaki Atoll (3˚43'S., 170˚43'W.) aka Phoenix Island is a treeless, triangular, coral atoll surrounded, except for the middle third of the W or longest side, by a wide platform reef. The reef bares at LW. Depths of less than 9.1m are found within 0.25 mile of the SE and NE sides. Shoals, which break heavily, extend about 0.4 mile off the NW end of the island. The land rim is about 4.9m high, 30m inshore from the reef. The first rise is covered with loose coral fragments washed in from the sea. The island is uninhabited. It is a wildlife sanctuary. Phoenix Island has been reported to give good radar returns up to 11 miles.

Winds—Weather.—Winds are always E. Usually, they vary from ENE to ESE, with the latter predominating.

Tides—Currents.—The current sets strongly past the N and S points of the island, converging on the W side. Close in to the shore on the W side of the island, the flood sets N and the ebb sets S. Offshore, the set is W about 0.5 knot, varying in strength and direction with the surface currents set up by the prevailing wind. (SD Pub-126)

This took about 1-hour to digitize, convert into a map, copy images, post to Flickr and finally post to EVS-Islands. The northwestern part of the island is obscured by clouds. I could detect the faint outline of the island proper, but I guessed on the shape of the beach.


Labels: , , , , , , , ,

posted by Mr Minton at 11:15 AM 0 comments