GeoTiff <-> Proj.4
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GeoTiff <-> Proj.4
by support.mn
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Hello,
There is no general rule how to map GeoTiff GeoKeys to proj.4 parameters (or is there?) Every projection has it's own mapping? Can I write "lat_ts" instead of "lat_0" ?? Is there "lon_ts"? Here I have those keys I have found some mapping, but how about the others. Must be different for each projection? ---------- ProjLinearUnitSizeGeoKey 3077 in meters ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1 ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2 ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0 ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0 ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit ProjCenterLongGeoKey 3088 in GeogAngularUnit ProjCenterLatGeoKey 3089 in GeogAngularUnit ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0 ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0 ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits ProjFalseOriginNorthingGeoKey 3087 in ProjLinearUnits ProjCenterEastingGeoKey 3090 in ProjLinearUnits ProjCenterNorthingGeoKey 3091 in ProjLinearUnits ProjScaleAtOriginGeoKey 3092 in ratio -> k_0 ProjScaleAtCenterGeoKey 3093 in ratio ProjAzimuthAngleGeoKey 3094 in GeogAzimuthUnit -> alpha ProjStraightVertPoleLongGeoKey 3095 in GeogAngularUnit ProjRectifiedGridAngleGeoKey 3096 in GeogAngularUnit ------------- Regards: Janne. _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Gerald I. Evenden-3
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On Wednesday 01 October 2008 10:08:12 am support.mn@... wrote:
> Hello, > > There is no general rule how to map GeoTiff GeoKeys to proj.4 > parameters (or is there?) Every projection has it's own mapping? > > Can I write "lat_ts" instead of "lat_0" ?? lat_ts denotes latitude of true scale while lat_0 generally refers to latitude of origin. One should *never* assume that they create the same value. > Is there "lon_ts"? I have never used it. "Longitude of true scale" is a meaningless term. > Here I have those keys I have found some mapping, > but how about the others. Must be different for each > projection? > > ---------- > > ProjLinearUnitSizeGeoKey 3077 in meters > > ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1 > ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2 > ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0 > ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0 > ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit > ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit > ProjCenterLongGeoKey 3088 in GeogAngularUnit > ProjCenterLatGeoKey 3089 in GeogAngularUnit > > ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0 > ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0 > ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits > ProjFalseOriginNorthingGeoKey 3087 in ProjLinearUnits > ProjCenterEastingGeoKey 3090 in ProjLinearUnits > ProjCenterNorthingGeoKey 3091 in ProjLinearUnits > > ProjScaleAtOriginGeoKey 3092 in ratio -> k_0 > ProjScaleAtCenterGeoKey 3093 in ratio > > ProjAzimuthAngleGeoKey 3094 in GeogAzimuthUnit -> alpha > ProjStraightVertPoleLongGeoKey 3095 in GeogAngularUnit > ProjRectifiedGridAngleGeoKey 3096 in GeogAngularUnit What a mish-mash of terminology. That is why I believe that the equations for the projection should be mandated as part of any projection description because they resolve the usage and meaning of control contants. And I suspect that the above often have different "flavors" of description in French, German, Italian, Russian, Chinese, etc.. Again, the mathematical description is the only lingua franca of the definition. -- The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum. -- Havelock Ellis (1859-1939) British psychologist _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Frank Warmerdam-2
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On Wed, Oct 1, 2008 at 4:08 PM, <support.mn@...> wrote:
> Hello, > > There is no general rule how to map GeoTiff GeoKeys to proj.4 > parameters (or is there?) Every projection has it's own mapping? Janne, The page at: http://geotiff.maptools.org/proj_list/ represents a "best effort" attempt to document the correlation between geotiff definitions and proj.4 (as well as EPSG and OGC WKT). Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@... light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Gerald I. Evenden-3
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On Thursday 02 October 2008 9:14:13 am support.mn@... wrote:
> Frank Warmerdam <warmerdam@...> kirjoitti: > > The page at: > > > > http://geotiff.maptools.org/proj_list/ > > > > represents a "best effort" attempt to document the > > correlation between geotiff definitions and proj.4 > > (as well as EPSG and OGC WKT). I have already added some comments (probably unwelcome) about the contents of the above web site although I do issue kudos for the thought and effort behind it. First, I detest the term "natural origin." It seems to be synonymous with the basic mathematical origin. "Natural" is an unnecessary adjective and just the term origin should suffice. The projection origin can be "shifted" in either geographic or Cartesian space by respective use of lon_0 and sometimes lat_0 and false easting and northing (x_0 and y_0). Use of lon_0 is ubiquitous among all types of projection usage and false easting/northing are universal among grid system specifications. lat_0 is sometimes ambiguous because it may actually specify the principle origin as in the case of many oblique projections. But this may also be viewed as a simple shift like lon_0. But use of lat_0 in normal cylindrical projections is exactly equivalent to using false northing. In most grid system cases that I am aware of, false northing is used rather than lat_0. Lastly, I cannot understand why it was necessary to include all the formulas for determining shift of the Cartesian coordinates when it is such a simple operation using [l]proj. For example: Mercator projection with origin for a map centered at CM 90w and with false origin located at 92W,33N. First: gie@charon:~$ lproj +proj=merc +ellps=WGS84 +lon_0=-90 -f '%.4f' -92 33 -222638.9816 3872033.7329 ^D >From the above numbers: gie@charon:~$ lproj +proj=merc +ellps=WGS84 +lon_0=-90 \ +x_0=222638.9816 +y_0=-3872033.7329 -92 33 0.00 -0.00 -90 35 222638.98 267339.03 ^D The only thing "tricky" was to expand the output precision of the first pass to ensure that short precision would not show up in the cm precision of the final operations. They still did with the -0.00 but ... . Is that not simpler than the material in the mercator_2sp.html page? When designing a grid system one only needs the easting and northing to be positive so the above numbers would probably be altered to: > Yes, I have been reading that. There seem to be several > problematic projecions. "Omerc" number 3, 4 and 5 in > GeoTiff does not import to Proj4 at all, or does it? > > Geotiff number 6, "merc" is not used at all? Or should not > be used? > > Geotiff number 15, "stere" uses "lat_0=CenterLat", not > mentioned? Or is it only intergraph? > > Geotiff number 27, "tmerc" soth oriented can not be used > directly, unless you turn all signs somewhere using extra > "ifs"? Isn't that forbidden, to have a south orientated map? > How the people know where the north is if that is upside > down? > > And Intergraph is using mostly different fields instead of > those given in your link? > > --------- > > Linear names are easy: whatever given ->x_0 and y_0 > > Ratio names also easy: whatever given -> k_0 > > Angular names are most difficult and all are not using same > names? There is no general rule? Ok. I make a mapping > table for the names then. > > ---------- > > BTW: There is couble of typos. Lcc(1) and Lcc(2) are entered > both as number 9. I am assuming that Lcc(2) is number 8 and > Lcc(1) is number 9? > > Regards: Janne. > > _______________________________________________ > Proj mailing list > Proj@... > http://lists.maptools.org/mailman/listinfo/proj -- The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum. -- Havelock Ellis (1859-1939) British psychologist _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Gerald I. Evenden-3
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On Thursday 02 October 2008 9:14:13 am support.mn@... wrote:
> Frank Warmerdam <warmerdam@...> kirjoitti: > > The page at: > > > > http://geotiff.maptools.org/proj_list/ ''' Sorry about the truncated earlier reply to this email as I was interupted by the phone and accidentally hit "send." Sorry but the terminology of Mercator(1sp)---(2sp) freaks me out. And the need for two entries. > Geotiff number 15, "stere" uses "lat_0=CenterLat", not > mentioned? Or is it only intergraph? That usage of lat_0 was mentioned before. > Geotiff number 27, "tmerc" soth oriented can not be used > directly, unless you turn all signs somewhere using extra > "ifs"? Isn't that forbidden, to have a south orientated map? > How the people know where the north is if that is upside > down? I spent two weeks in Australia almost 40 years ago and don't remember everyone standing on their heads. Unfortunately, I do not remember seeing a map at the time so do not know if they plot them upside down. ;-) But I had a good time and even managed to survive driving on the wrong side. At the moment, the only place a south option is used is for UTM where a false northing of 10,000,000 meters is added when the +south option is spec'd. The issue of a 180 rotated Cartesian system for southern hemisphere usage has only come up recently and I am not sure how widespread this usage is nor, since a minus scale handles the problem, whether an added option is truly needed. Also is this upside down coordinates system part of a grid system? Are the maps printed with south up? > And Intergraph is using mostly different fields instead of > those given in your link? > > --------- > > Linear names are easy: whatever given ->x_0 and y_0 > > Ratio names also easy: whatever given -> k_0 Is the term "ratio" proper. I simply look at it as a unitless multiplier. > Angular names are most difficult and all are not using same > names? There is no general rule? Ok. I make a mapping > table for the names then. > > ---------- > > BTW: There is couble of typos. Lcc(1) and Lcc(2) are entered > both as number 9. I am assuming that Lcc(2) is number 8 and > Lcc(1) is number 9? ... I would like to add: where did this Laborde Oblique Mercator come from? Are there any spec for it? From Mugnier, it is basically the same operations in the general case as previously discussed in the special case of Gauss-Schreiber (Laborde) projection. From the above web site entry for Laborde Oblique Mercator: EPSG Notes Can be accomodated by Oblique Mercator method (code 9815). 9815 make the statement: Notes The formula is exactly the same as for Hotine Oblique Mercator. I consider this to be an alias for that projection. See it for details on formula. WRONG. The problem is that this erroneous position is pandemic with Transverse Mercator. This issue of Swiss "oblique mercator" is the most universally screwed up problem. The only site I have seen that seems to have a handle on it is the Swiss and as they portray it is simply a Mercator rotated such that the axis of the pole of the projection is in the merdianal plane of the projection and that the equator of the projection passes through the central parallel. And it uses the Gauss conformal transformation to a sphere as an intermediate step. *THUS* it is *NOT* a Hotine projection. Somewhere, someone came along and also established a Hotine projection for Swiss imaging applications. WHY? Probably because they did not have a clue as to the original Swiss projection and then just assumed that because "oblique" was in its name it must be Hotine. WE ARE IN DESPERATE NEED OF A COMPREHENSIVE, ACCURATE AND RELIABLE REFERENCE OF CARTOGRAPHIC PROJECTIONS. Yes, I am yelling. -- The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum. -- Havelock Ellis (1859-1939) British psychologist _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Terminology for origins
by Mikael Rittri-2
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Is there a simple and accepted standard terminology for the various kinds of projection origins?
Gerald wrote: > First, I detest the term "natural origin." Me too. > It seems to be synonymous with the basic mathematical origin. "Natural" is an unnecessary adjective I agree that it is the wrong adjective. > and just the term origin should suffice. Should suffice, but doesn't, since the point with Easting and Northing both zero is also a kind of origin. I think there used to be a simple and wide-spread terminology before EPSG became so influential, like this: * False Origin: the point whose projected coordinates are both zero. * True Origin: the point whose projected coordinates are False Easting and False Northing. The words "True" and "False" are perhaps somewhat strange, but this terminology is used, for example, by: - http://www.mered.org.uk/mike/gps/gps_usergrid_more.htm - http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystemsinfo/guidecontents/guide7.html - http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys.html - http://home.clear.net.nz/pages/paulcatc/nzgrid1.htm - http://www.dartmouth.edu/~remsense/1-10%20Projections.htm On the other hand, we have a single but influential source, - http://www.epsg.org/guides/docs/G7-2.pdf (EPSG (or OGP) Guidance Note 7.2) which makes subtle (I say hair-splitting) distinctions. It defines (section 1.2) * Grid Origin: the point whose projected coordinates are both zero. which I can accept, but also that * The point whose projected coordinates are False Easting and False Northing should be called o "Natural Origin" if it is natural enough in an undefined way, or o "False Origin" if it is less natural, or o "Projection Centre", if it is not very natural, but not very false either, o "Grid Origin", but in a different meaning from the usual EPSG Grid Origin, if the other alternatives are not sufficiently confusing ;-) In practice, it seems that this point is called o "Natural Origin" in most projections, but o "False Origin" in a Lambert Conformal Conic (2SP) and in a Polar Stereographic Variant C, o "Projection Centre" in an Oblique Mercator (plain or non-Hotine variant), o "Grid Origin" in a Krovak Oblique Conformal Conic. The first three lines above follows mostly from Table 3 on page 14. Krovak is forgotten in Table 3, but in section 1.3.2 on Krovak names the parameters FE = Easting at grid origin, FN = Northing at grid origin, even though according to section 1.2, the Easting and Northing at a Grid Origin have to be zero and are not free to vary. (In earlier versions of Guidance Note 7.2, these parameters for Krovak were called Easting/Northing at Projection Centre, but this was wrong. In the usual instance of projection, the Projection Centre is east of Slovakia, but the point with coordinates FE and FN is the oblique cone apex near Helsinki.) Personally, I prefer the old, simple terminology, but since EPSG has hijacked the old term "False Origin" to mean "True Origin" now and then, the old terminology can be misunderstood. Grid Origin is OK by me, since it cannot be misunderstood (except for Krovak!). For the point with coordinates (FE, FN), I don't know a really good name. However, the site http://www.sco.wisc.edu/pubs/wiscoord/summary.php uses the term "Actual Origin" for this point, which does not conflict with any EPSG term. Does anyone agree that Grid Origin and Actual Origin are good names? -- Mikael Rittri Carmenta AB Box 11354 SE-404 28 Göteborg Visitors: Sankt Eriksgatan 5 SWEDEN Tel: +46-31-775 57 37 Mob: +46-703-60 34 07 mikael.rittri@... www.carmenta.com _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Frank Warmerdam-2
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On Thu, Oct 2, 2008 at 5:32 PM, Gerald I. Evenden
<geraldi.evenden@...> wrote: > On Thursday 02 October 2008 9:14:13 am support.mn@... wrote: >> Frank Warmerdam <warmerdam@...> kirjoitti: >> > The page at: >> > >> > http://geotiff.maptools.org/proj_list/ >> > >> > represents a "best effort" attempt to document the >> > correlation between geotiff definitions and proj.4 >> > (as well as EPSG and OGC WKT). > > I have already added some comments (probably unwelcome) about the contents of > the above web site although I do issue kudos for the thought and effort > behind it. Gerald, I would stress that the size terminology is based on EPSG terms, and EPSG is the basis of GeoTIFF (for better or worse). I shall mark your and Janne's email for future reiew, but even if I am able to correct a few things I won't be attempting to address the terminology question. > WE ARE IN DESPERATE NEED OF A COMPREHENSIVE, ACCURATE > AND RELIABLE REFERENCE OF CARTOGRAPHIC PROJECTIONS. I would love for such a thing to exist in a form that can be easily related to various software systems and file formats. I would love to see such an effort attacked as a "MetaCRS" effort - that is collaboratively amoung the various experts here, the CS-Map community and some of the other OSGeo coordinate system efforts (ie. GeoTools). Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@... light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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RE: Terminology for origins
by Clifford J Mugnier
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In North Africa, several of the Grids also have a False Northing at the False Origin in order to avoid negative northings.
Really!
:-)
Snyder's terminology explicitly referred to Grids only in the United States and used by the U.S. Geological Survey. Others have adopted his terms and mistakenly applied them to other countries and regions. For the most part, the old British General Staff, Geographic Section from WWII really defined practically all of the components of existing Grids. When Snyder had questions about large-scale coordinate systems, he commonly referenced me. For the proper terminology in English, I'd defer to the current British Military Survey as the final authoritative source. The U.S. Military has really cobbled up an awful collection of erroneous terms.
Lord help you for the equivalent terms in other languages ... French is a particular zinger because their terms seem to have zero relation to the English terms. Castilian Spanish would likely be a similar enigma.
For instance, the original uses for the following terms were:
Grid - Aphylactic projections ( Cassini-Soldner, Polyhedric, Polyconic)
Zone - Lambert Conformal Conic & Ellipsoidal Bonne
Belt - Transverse Mercator
Cartesian systems for the Oblique Mercator, the Krovak, the Rosenmund, the Hatt did not have explicit terms.
Since then, such things have eventually been considered to be synonomous. Once upon a time, they were not.
Cliff Mugnier
LSU From: proj-bounces@... on behalf of Mikael Rittri Sent: Fri 03-Oct-08 03:34 To: geraldi.evenden@...; PROJ.4 and general Projections Discussions Subject: [Proj] Terminology for origins Is there a simple and accepted standard terminology for the various kinds of projection origins? _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Terminology for origins, and everything
by Gerald I. Evenden-3
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The problems with the variety of nomenclatures is going to persist until some
lingua franca of cartography is established. If I recall correctly, if you are a pilot that flies internationally, all you need to know is English to communicate with any airport control tower. Similarly we need something similar restriction for describing cartographic projections. In the case of origins I feel the case is simply: 1. Designate the names of the two coordinate systems involved such as geographic and Cartesian. A "projection" transforms information in one coordinate system to and from the alternate system. For this case the coordinate systems axis are called latitude and longitude for the geographic system and easting and northing for the Cartesian system. 2. If "base" geographic coordinates, lat_0 or lon_0, are specified then they represent the location in geographic space of the Cartesian system origin. When either lat_0 or lon_0 are not specified then they are respectively assumed to have a 0 value unless otherwise specified. Other projection conditions that may be caused by their usage require additional description. 3. "False" eastings and northings are values that are added to the respective easting and northing coordinates and thus offset the coordinates from their origin. Usage is normally restricted to grid systems in order to maintain positive Cartesian values over the region of application. Omission denotes 0 values. This is a suggested starter. Something for heated debate and resolution. I, for one, wish to refine item 1. into parts that refine the use of the term "projection" so as to ensure that it does not expand to include other issues. A strict use of the meaning of "cartographic projection." This is obviously reminiscent of much earlier debates of including datum shifts into proj, etc.. ;-) An interesting factor about item 2. is that one projection prohibits (or ignores in proj's case) the specification of lat_0: UTM. My terminology for geographic and Cartesian are certainly open. Etc., etc.. -- The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum. -- Havelock Ellis (1859-1939) British psychologist _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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Re: GeoTiff <-> Proj.4
by Gerald I. Evenden-3
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On Friday 03 October 2008 11:25:47 am support.mn@... wrote:
> Hello, > > I am still asking if it is totally not possible to use omerc to decode > GeoTiff projections 3,4 and 5. The problem seems to be wha to do with the ... > http://en.wikipedia.org/wiki/American_National_Standards_Institute I first thought was: "what a good idea," but skimming on to ISO reference the criticism section brought up the cost involved and that reminded me of a long ago experience. I thought it would be a good idea to get a copy of the ANSI C standards but suddenly ran into the $$$ for a copy. > More about Geotiff <-> Proj.4: > > Ref 1: > http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_2sp. >html > > Ref 2: > http://www.remotesensing.org/geotiff/spec/geotiff3.html#3.1.3. > > Ref 1 gives: > > +proj=lcc > +lat_1=Latitude of first standard parallel > +lat_2=Latitude of second standard parallel They should really be called the secant parallels. There is nothing "standard" about them. The alternate lcc is to specify the parallel of tangency and then k_0 which does the same thing. > +lat_0=Latitude of false origin > +lon_0=Longitude of false origin Oh, please! "of false origin" good grief. > +x_0=False Origin Easting > +y_0=False Origin Northing > > Ref 2 gives: > > +proj=lcc > +lat_1=Latitude of first standard parallel > +lat_2=Latitude of second standard parallel > +lat_0=Latitude of natural origin (ProjNatOriginLatGeoKey) > +lon_0=Longitude of projection center (ProjCenterLongGeoKey) > +x_0=False Origin Easting > +y_0=False Origin Northing Terrible, terrible. Proj may have also been guilty of the "standard" part. > I am starting to belive that best way to deal with the problem is to first > allocate lat_1, lat2, lat_ts and then start to look after any lat or lon > and put them to lat_0 and lon_0. Since every creator of GeoTiff files puts > them randomly somwhere what is left. lat_ts is not involved with conics. Is there an editor or editing group associated with these sites? > Regards Janne. -- The whole religious complexion of the modern world is due to the absence from Jerusalem of a lunatic asylum. -- Havelock Ellis (1859-1939) British psychologist _______________________________________________ Proj mailing list Proj@... http://lists.maptools.org/mailman/listinfo/proj |
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RE: Terminology for origins
by Mikael Rittri-2
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