Struve Geodetic Arc

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The Struve Geodetic Arc is a chain of triangulation stretching more or less down the 26° E line of longitude from near Hammerfest on the Arctic Ocean over 2,820 km south to Izmail on the Black Sea. The survey was carried out between 1816 and 1855 under the guidance of F.G.W. Struve.

Theoretically, a degree of latitude is a constant and would have the same value at the equator as at the pole. But already Isaac Newton believed that the Earth was slightly flattened at the poles. This question of the shape and size of the Earth inspired the astronomer Friedrich George Wilhern Struve to come up with his famous Meridian Arc measurement.

The scheme included 258 main triangles with 265 not and over 60 subsidiary station points.The selection of points involves a total of 34 sites on the Struve Geodetic Arc. In today’s geography. the Arc passes through ten countries, viz. Norway (4 station points), Sweden (4), Finland (6), the Russian Federation (2), Estonia (3). Latvia (2). Lithuania (3). Belarus (5), the Republic of Moldova (1), and Ukraine (4).

All of the points in the Arc were designated as UNESCO World Heritage sites in 2005.

The site at Puolakka is easily accessible from central Finland, for example from Tampere, or especially Jyväskylä.

There is parking at the start of the walk, which is not maintained during the winter. But there is ample space on the roadside for parking. The path itself was in good condition but the road to the start could be difficult after a heavy snowfall.

The walk itself is 1km, all uphill. The path is very well maintained with stairs for the steeper sections. The view is definitely worth the time to visit.

740 meters to the start and 260 to the lookout tower

Walk path:

Mapping Strava Data

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In 2018 we started a running club at work.

I created a quick script to parse the data on Strava to a ShapeFile, which can be easily animated with QGIS.

The script only works with Garmin files, GPX, TCX, and FIT.

Source: https://github.com/HeikkiVesanto/Strava-Garmin-Parser

Example:

OpenStreetMap Ireland 2018 Visualized

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2018 was a very productive year for OpenStreetMap in Ireland.

Around 70k nodes added, 60k ways added, and 160k polygons added.

Finally a company was formed to facilitate becoming a fully fledged local chapter.

What does that look like day to day:

Copying Rasters in PostGIS

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I ran into a process where I wanted to create copies of rasters in PostgreSQL. While seemingly a simple process this took me a bit of work to figure out.

For my workflow I had three rasters, which all have the same size, and I want to load them into the same PostGIS table with three raster geometry columns. I don’t think this will work for different sized rasters since the rid’s will not match.

Three rasters:
raster1 raster2 raster3

Which I want to copy into:
merged_raster

First to create the merged raster table:

CREATE TABLE merged_raster
(
  rid serial NOT NULL,
  raster1 raster,
  raster2 raster,
  raster3 raster
);

CREATE TABLE merged_raster

(

rid serial NOT NULL,

raster1 raster,

raster2 raster,

raster3 raster

);

Then to add the rid’s. These are the id’s of the tiles that the raster was split into when loading. If your tile size is large enough then you may only have one.

INSERT INTO merged_raster(rid)
(SELECT rid FROM raster1);

1 2	INSERT INTO merged_raster(rid) (SELECT rid FROM raster1);

Then copying the actual data is straighforward (this assumes the raster column in the raster1 datasets is called rast):

UPDATE merged_raster m
SET raster1 = r.rast
FROM raster1 r
WHERE r.rid = m.rid;

UPDATE merged_raster m
SET raster2 = r.rast
FROM raster2 r
WHERE r.rid = m.rid;

UPDATE merged_raster m
SET raster3 = r.rast
FROM raster3 r
WHERE r.rid = m.rid;