Getting coordinates from shapefile

Question

I have a .shp file (downloaded from here), but it is a bunch of pink lines (I expected something like a bunch of dots or something and I have to transform it into gps coordinates (which I guess it's a .gpx file), but I have a lot of trouble finding the tools to do so and understanding what everything means. Right now I'm using QGIS, and I think once I have the coordinates I should dump the values into PostGIS. Could you guys point me in the right direction about which tools I should use, how or tips about how to do things the right way?

Further explanation: I want to get coordinate points that "shape" the coastline, so given a house's position, it can tell you how far away the coast is from the house.

Edit: I managed to get some stuff with QGIS "extract nodes" option, but I don't see any use for this data:

Shape_Leng,Shape_Area
309.72983208000,4079.18723489000
309.72983208000,4079.18723489000

Values repeat a lot and they don't look like map coordinates. What went wrong?

Answer 1

If you want to extract the vertices go Vector->Geometry Tools->Extract nodes.

However, if you want to simply import a shapefile into PostGIS you can do it in one go (you don't have to convert to points unless you want to). Use shp2pgsql. This tool will be helpful whether you want the points or the lines. Do a search on this site for more information on both topics here.

EDIT:
Following the comments above, have a look here to get you started on 'how things work'. Also - for your situation you will want the line, so do not extract just the points. So simply use shp2pgsql to load your shapefile into postgis. That's all you need to do. Then in PostGIS, ensure you have a spatial index

CREATE INDEX coastline_gidx on coastline USING GIST(geometry)

Then, depending on your exact use-case, consider using ST_DWithin or ST_Distance to test for the distance (other distance tools are also available so check the documentation).

Answer 2

This question breaks down into a few questions questions,

1. How do I geocode to get a coordinate-POINT from a house's position?

2. Given an arbitrary POINT and a LINESTRING, what is the nearest point on the string?

   This is answered simply with a ST_Line_Locate_Point followed by a call to ST_Line_Interpolate_Point.

3. Given two points how do I find the distance between them?

   This is answered with a simple call to ST_Distance(pt1::geography, pt2::geography).