Projects/Marble/NaturalEarth - Revision history

Tackat: /* Description of the file format */

2012-07-22T11:38:58Z

‎Description of the file format

Tackat: /* File Structure */

2012-07-22T11:35:51Z

‎File Structure

Tackat: /* Description of the file format */

2012-07-22T11:35:23Z

‎Description of the file format

Tackat: /* Description of the file format */

2012-07-22T11:24:46Z

‎Description of the file format

Tackat: /* Possible new file format */

2012-07-22T11:22:47Z

‎Possible new file format

Odysseus: /* Spatialite */

2012-05-01T11:33:15Z

‎Spatialite

Odysseus: /* Spatialite */

2012-05-01T11:23:45Z

‎Spatialite

Odysseus: /* Attribute Database */

2012-05-01T11:23:04Z

‎Attribute Database

Earthwings: /* Action Plan */

2012-04-09T09:59:16Z

‎Action Plan

Odysseus: /* Action Plan */

2011-03-22T17:00:59Z

‎Action Plan

@@ Line 106: / Line 106: @@
 In the fileformat initally a file header is provided that provides the file format version and the number of polygons stored inside the file. A Polygon starts with the Polygon Header which provides the feature id and the number of so called "absolute nodes" that are about to follow. Absolute nodes always contain absolute geodetic coordinates. The Polygon Header also provides a flag that allows to specify whether the polygon is supposed to represent a line string ("0") or a linear ring ("1").
-Absolute nodes can be followed by relative nodes: These relative nodes are always nodes that follow in correct order after each absolute node in the polygon.
+Each absolute node can be followed by relative nodes: These relative nodes are always nodes that follow in correct order inside the polygon after "their" absolute node.
-Each absolute node specifies the number of relative nodes which contain relative coordinates in reference to their absolute node. Each absolute node is followed by its relative nodes. So an absolute node provides the absolute reference for child nodes across a theoretical area of 2x2 squaredegree-area (which in practice frequently might rather amount to 1x1 square degrees).
+Each absolute node specifies the number of relative nodes which contain relative coordinates in reference to their absolute node. So an absolute node provides the absolute reference for relative nodes across a theoretical area of 2x2 squaredegree-area (which in practice frequently might rather amount to 1x1 square degrees).
 So much of the compression works by just referencing lat/lon diffs to special "absolute nodes". Hence the compression will especially work well for polygons with many nodes with a high node density.

@@ Line 126: / Line 126: @@
 * quint8: Flags: 1st bit: polygonIsClosed
-'''Parent node chunk'''
+'''Absolute node chunk'''
 * qint16: Latitude in halfarcminutes (allowed range = [-10800;+10800 ] halfarcminutes = [-90;+90 ] degrees )
@@ Line 132: / Line 132: @@
 * qint16: Number of child node chunks to follow (equals "0" if there are no child nodes)
-'''Child node chunk'''
+'''Relative node chunk'''
 * qint8: Latitude-diff in halfarcminutes compared to the parent (allowed range = [-60;+60] arcminutes = [-1;+1]  degrees)

@@ Line 105: / Line 105: @@
 =====Description of the file format=====
-In the fileformat initally a file header is provided that provides the file format version and the number of polygons stored inside the file. A Polygon starts with the Polygon Header which provides the feature id and the number of so called "parent node chunks" that are about to follow. Parent node chunks always contain absolute geodetic coordinates. The Polygon Header also provides a flag that allows to specify whether the polygon is supposed to represent a line string ("0") or a linear ring ("1").
+In the fileformat initally a file header is provided that provides the file format version and the number of polygons stored inside the file. A Polygon starts with the Polygon Header which provides the feature id and the number of so called "absolute nodes" that are about to follow. Absolute nodes always contain absolute geodetic coordinates. The Polygon Header also provides a flag that allows to specify whether the polygon is supposed to represent a line string ("0") or a linear ring ("1").
-Parent nodes can be followed by child nodes: These child nodes are always nodes that follow in correct order the after the parent node in the polygon.
+Absolute nodes can be followed by relative nodes: These relative nodes are always nodes that follow in correct order after each absolute node in the polygon.
-Each parent node specifies the number of child nodes which contain relative coordinates in reference to the parent. Each parent node is followed by its child nodes which just specify the difference in terms of coordinates compared to their parent node. So a parent node provides the absolute reference for child nodes across a theoretical area of 2x2 squaredegree-area (which in practice frequently might rather amount to 1x1 square degrees).
+Each absolute node specifies the number of relative nodes which contain relative coordinates in reference to their absolute node. Each absolute node is followed by its relative nodes. So an absolute node provides the absolute reference for child nodes across a theoretical area of 2x2 squaredegree-area (which in practice frequently might rather amount to 1x1 square degrees).
-So much of the compression works by just referencing lat/lon diffs to special "parent nodes". Hence the compression will especially work well for polygons with many nodes with a high node density.
+So much of the compression works by just referencing lat/lon diffs to special "absolute nodes". Hence the compression will especially work well for polygons with many nodes with a high node density.
 The parser has to convert these relative coordinates to absolute coordinates.

@@ Line 105: / Line 105: @@
 =====Description of the file format=====
-In the fileformat initally a file header is provided that provides the file format version and the number of polygons stored inside the file. A Polygon starts with the Polygon Header which provides the feature id and the number of parent node chunks (which contain absolute geodetic coordinates) that are about to follow. The Polygon Header also provides a flag that allows to specify whether the polygon is supposed to represent a line string ("0") or a linear ring ("1").
+In the fileformat initally a file header is provided that provides the file format version and the number of polygons stored inside the file. A Polygon starts with the Polygon Header which provides the feature id and the number of so called "parent node chunks" that are about to follow. Parent node chunks always contain absolute geodetic coordinates. The Polygon Header also provides a flag that allows to specify whether the polygon is supposed to represent a line string ("0") or a linear ring ("1").
 Parent nodes can be followed by child nodes: These child nodes are always nodes that follow in correct order the after the parent node in the polygon.
 Each parent node specifies the number of child nodes which contain relative coordinates in reference to the parent. Each parent node is followed by its child nodes which just specify the difference in terms of coordinates compared to their parent node. So a parent node provides the absolute reference for child nodes across a theoretical area of 2x2 squaredegree-area (which in practice frequently might rather amount to 1x1 square degrees).

@@ Line 86: / Line 86: @@
 * Would benefit all vector formats, e.g. kml, ppx, shp
-==== Possible new file format ====
+==== Possible new file format (Proposed by John) ====
 Potential new Marble file format based on PNT:
 * 1st integer (32 bit): Latitude in arcseconds highest bit indicates new polygon starts: header information has to be read from 3rd integer
@@ Line 97: / Line 97: @@
 * Roughly 533,202 x 8 bytes = 4 Mb for the country borders alone, not including internal border and coastline files
 * If that's too much to ship, then ship the 1:50m dataset as the default and download the 1:10m dataset once online
 ==== Attribute Database ====

@@ Line 116: / Line 116: @@
 There is a 20Mb zip file available for Natural Earth in Spatialite format, it is unclear how much of Natural Earth is contained in this.  A minimal dataset could be shipped by default with the full dataset downloaded later.
-Spatial SQL queries could return just those vectors currently in the viewport, but repeated reloading and redrawing could be inefficent.  However this may also solve the Level-of-Detail problem.
+Spatial SQL queries could return just those vectors currently in the viewport, but repeated reloading and redrawing could be inefficient.  However this may also solve the Level-of-Detail problem.
 More research is required here.  It may not be a suitable option for the default Atlas view, but would be a very powerful extension for Marble to provide lightweight GIS-like functionality.

@@ Line 110: / Line 110: @@
 and we wouldn't be reliant on Geonames IDs staying constant or being online.
-=== Spatialite ===
+==== Spatialite ====
 One option would be to integrate Spatialite and use this as both the data storage for the vectors and as the attribute database.  Spatialite is an extension to SQLite implementing a Spatial SQL database.  Among the feature this provides is a compact data storage format and the ability to import Shapefiles and CSV files, as well as access all the standard GEOS tools if installed.

@@ Line 109: / Line 109: @@
 to provide).  This would allow look-ups via whatever code or ID is available,
 and we wouldn't be reliant on Geonames IDs staying constant or being online.
 === Action Plan ===

@@ Line 114: / Line 114: @@
 A possible action plan is
 # Fix GeoPainter LinearRings which contain a pole not rendered correctly
-# Implement Douglas-Peuker reduction in GeoDataLineString
+# Implement Douglas-Peucker reduction in GeoDataLineString
 # New PNT file format definition (with a different name, MBL?)
 # Metadata file format definition

@@ Line 118: / Line 118: @@
 # Metadata file format definition
 # New GeoData PNT2 file loading code (convert old data).
-# shp2pnt2 script to convert shp to new formats (using Perl::shp? there's
+# shp2pnt2 script to convert shp to new formats (using Perl::shp? there's shp2xxx scripts out there we could copy?), including matching to Geonames ID
-shp2xxx scripts out there we could copy?), including matching to Geonames ID
+# split files into 'ship with', 'download asap', 'ghns'
-# split files into 'ship with', 'download asap', 'ghns'@
 Later add simple shapefile loading to GeoData, maybe with attibute layer?