EVS-Islands

To make sense out of these 4-images it is best to left click, select "All Sizes" and study the original sized image.

I think the PGS (Prototype Global Shoreline) has the potential to be even better than what it will ultimately become. The algorithm used to generate the vectors used "Short Wave Infra-Red (SWIR) bands which provided the best shoreline delineation and an accuracy of about 50-meters". (See NGA White Paper). Correct! PGS is a major improvement over WVS.

PGS is what I have long discussed as my ambition, "to create an Enhanced Vector Shoreline" map of the world". Using Landsat-7 imagery, I would generate shorelines. And that is exactly what EarthSat has done. They have taken Landsat-7 ETM+ 2000 imagery and generated a Global Shoreline. At first look, it is impressive. Especially when you compare to WVS vectors (See previous post). At second look, it is still impressive. EarthSat has created a world shoreline that NGA makes available at NO COST! At third look, PGS can be better - EVS Precision.

Working with 2-sections of shoreline in Central America, I determined how much adjusting would be required to enhance PGS to an EVS level of precision.

38% of the vectices (49) had to be adjusted. The adjustments were small, a few millimeters, but when completed they transformed a very good shoreline into an excellent shoreline - EVS Precision. 5% (6) of the vectices were deleted. These were deemed,by me, to be unneccessary toward generating a quality product. Parts of the PGS shoreline contain strings of vectices that appear to be a programming anomoly. There are 8 to 10 vertices strung together along a 2-centimeter straight line. So, I deleted the extra vertices to correct the overplots.

OT: How To

Posted by Mr Minton at 6/24/2006 08:00:00 AM | Permalink | Comments | links to this post

Let me begin by advising that you left-click on the image and then select "All Sizes" to see this image in it's full size. This shows 4-vector shorelines. They all have their benefits. WVS is the least defined of the four. It was built from 1:250,000 Tactical Pilotage Charts and Nautical Charts. Much of the data was pre-satellite. It is good for work above 1:250,000 scale.

The PGS is shoreline data extracted from Landsat ETM+ 2000 imagery. It is a very recent entry into precise shorelines. Once the obscured shorelines are resolved it will be an exceptional vector map file of the world.

EVS is my designation for shorelines created from Landsat ETM+ 2000. I have demonstrated in previous posts that althought the PGS is a wonderful world map file it does not match to precision of EVS maps. My hand-drawn maps are some of the best made for many islands throughout the world.

Now for GEVS (Google Earth Vector Shorelines), they are a tremendous improvement over EVS shorelines. Because much of the imagery is 1-meter resolution, the shoreline plots are extremely precise. I still haven't figured out on how to incorporate other layers of information I typically digitize. As I work with GEVS I am sure I will develop a system that will allow me to capture additional layers of information, besides shorelines.

All 4-vector shoreline files work for different purposes. My island maps will still make great use of the Landsat ETM+ 2000 imagery. At times, I will execute mapping projects using 1-meter imagery. Ain't mapping fun? So many choices.

OT: Comparison

Posted by Mr Minton at 6/22/2006 04:49:00 PM | Permalink | Comments | links to this post

Adalar Islands are one of the primary sources of my intense interest in islands. I spent a wonderful summer on the main island of Buyukada back in 1965. The island was magical. No automobiles, only horse-drawn carriages to take you about the island. On the high point of the island is the site of a Greek Orthodox Catholic Monastary. The people I met were from all over Europe. It was a place that nationality was secondary to having a relaxing time. Oh, yes, the water was warm and crystal clear. Evenings were spent strolling about the island city to see and be seen. After dark, you could dance at the disco or view the outdoor movie theater. I am sure it has changed. I would still visit. These islands are tourist jewels and a definite "must-see" for the Istanbul visitor.

I redigitized some of the layers on Buyukada. The refining process took about 4-hours to complete. The new work was spent classifying vegetation more accurately. I realize I did not include a legend with this map.

Posted by Mr Minton at 6/20/2006 10:42:00 PM | Permalink | Comments | links to this post

Rose Atoll (14˚33'S., 168˚09'W.), the farthest E of the Samoa Islands, is nearly square in shape; its sides are about 1.5 miles in length. Sand Island, inside the reef on the N extremity, is merely a sand spot.

A large clump of trees, 20m high, stands on Rose Atoll.

There is a boat channel into the lagoon, close W of the N extremity of the reef.

Tides—Currents.—Tidal currents off Rose Atoll are reported to set NE and SW, with the SW or ebb current being the stronger.

Regulations.—Rose Atoll is a National Wildlife Refuge managed by the Department of Interior. Entry is strictly prohibited without prior approval.

(SD Pub-126)

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This was a very fast project. From start to finish was about 2-hours. The Landsat image does not do Rose Atoll justice. There is a site that is made up of Rose Atoll Photographs. The photos show a quiet place without the clutter of people.

Posted by Mr Minton at 6/19/2006 05:47:00 PM | Permalink | Comments | links to this post