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lionel

972 post(s)
#25-Apr-22 21:16

A) projection

What is the difference between Lat/Long and Web Mercator (georeference.org)

and sub link https://manifold.net/doc/mfd9/example__reproject_a_drawing.htm

i expect to be able to have access to the editor when click on item list in standard and EPSG tab but not , why even i only want to see text list in a form ( write mode disable) .

i think all projection must use a value for thoses variables :

{ "Name": "WGS 84 \/ NSIDC EASE-Grid 2.0 Global (EPSG:6933)", "System": "Lambert Cylindrical Equal Area", "CenterLat": 30, "CenterLon": 0, "Axes": "XY", "Base": "WGS 84 (EPSG:4326)", "MajorAxis": 6378137, "Eccentricity": 0.08181919084262149, "Unit": "Meter", "UnitScale": 1, "UnitShort": "m" }

Does the 2 projections below are the same except metric ?

Why not make viewable the Coordinate System Metrics explicitly ( even if 0) by using Label ?

but which of those items are relative to Datum , ellipsoid or other name

B) paste without metric

So paste do 2 things paste a coordinate system and PAste a coordinate system Metric !

Where are edit and save thoses 2 informations inside manifold ?

in which context we need to paste with or without metric ?

Thank's

Attachments:
coordinateSystemMEtric.png
pasteWithmetric.png
paste_doc.png
projection_difference.png


INFOGRAPHY union , LINK doc , API, deepl & keyboard shortcut

lionel

972 post(s)
#25-Apr-22 21:37

another question

1) if we copy a <geom area> content from a cell of a table and copy it to another cell of type <Geom Line> another table . How is process the copy , Does Geom Type contain some information other than list of points coordinates ( Y,Y,Z) or (Deg,Deg,Z) ?

1) Does content of Geom contain the same data information that data show when edit WKT ( only points coordinates) ?

thank's


INFOGRAPHY union , LINK doc , API, deepl & keyboard shortcut

adamw

10,011 post(s)
#18-May-22 08:30

A geom value contains the information regarding its type. If you copy an area geom into a cell which had a line geom, the line will be replaced with the area.

A geom value can contain more data than what could be conveyed with a WKT. For example, a geom can contain curvilinear segments that are not circular arcs (not supported by WKT), it can contain various options like those that describe branch ordering, etc.

adamw

10,011 post(s)
#18-May-22 08:28

The definition of the coordinate system on the Standard / EPSG tabs is read-only because it is only there for information, not for editing. If you want to edit specific parameters for the coordinate system, use the Custom tab. If you want to use, say, a EPSG system with some adjustments, first apply the EPSG system (select the system and press OK, closing the dialog), then edit the system again and adjust the parameters you want in the Custom tab.

You can see the parameters for the base coordinate system in the Base Coordinate System dialog, invoked if you press the edit button next to the base coordinate system. Out of those you bolded in the definition of the coordinate system, the base coordinate system is responsible for: Base, Eccentricity. There's also usually MajorAxis. For each parameter there is a default value that is used if the parameter is not present in the definition.

The definition of a coordinate system includes metrics which define scale / shift / unit. Scale and shift are normally used with images. Copying a coordinate system and pasting it without metrics is usually used when an image does not have information regarding its coordinate system (eg, there was no PRJ file or it was wrong) but does have proper scales / shifts (eg, there was a world file).

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