很久之前做过mmap的投影代码及图，不过当时自己水平也不行，无论是对图的理解还是对matlab的理解都不足。后来博客搬来搬去的，图也丢了，代码也挂了，正好最近又在用，所以重新做了一遍。
投影主要分四类
1、Azimuthal projection，方位角投影，默认图是圆形的。有的适合极地，有的适合看天球，保角和等面积的特性也不同。看需要了。利用‘rec’, 'on' 可以把圆形改为方形，多图拼接更美观
2、Cylindrical projections，柱状投影。正常就是方形图，具体的有的适合全球，有的适合很小范围。经纬圈也有的直线有的弯曲，弯曲的经线还可以通过clo 来设置图中甚至图外垂直经线的位置。倾斜型的还可以以地球的任意大圆为中心绘图。柱状图在两侧的变形是很厉害的，所以有的适合中纬度有的适合赤道。
3、Conic Projections，椎体投影。默认画的是同心圆环，但可以设置成方形图，就把周围多画点补成方的。适合中纬度地区，东西长条图
4、Miscellaneous global projection，传统全球图，各种漂亮
各个投影适合多大范围的图，大概怎么设置请参考具体代码和后面附图
m_map projections
%% m_map projections
clear;clc
clf
close all
proj = {... Azimuthal Projections
'Stereographic'; % 1 Polar regions
'Orthographic'; % 2 resembles the globe
'Azimuthal Equal-area'; % 3
'Azimuthal Equidistant'; % 4
'Gnomonic'; % 5
'Satellite'; % 6
... Cylindrical Projections
'Mercator'; % 7
'Miller Cylindrical'; % 8
'Equidistant Cylindrical'; % 9
'Oblique Mercator'; % 10
'Transverse Mercator'; % 11
'UTM'; % 12
'Sinusoidal'; % 13
'Gall-Peters'; % 14
... Conic Projections
'Albers Equal-Area Conic'; % 15
'Lambert Conformal Conic'; % 16
... Global Projections
'Hammer-Aitoff'; % 17
'Mollweide'; % 18
'Robinson'}; % 19
for kp = 1:19
disp(proj{kp})
name = [num2str(kp,'%02d'),' - ', proj{kp}];
switch kp
% Azimuthal Projections
case 1
% Stereographic
% conformal but not equal area, often used for polar regions
figure
m_proj(proj{kp},'lon', 10, 'lat', 85, 'rad', 25,'rec','on')
m_coast; m_grid;
case 2
% Orthographic
% neither equal nor conformal, resemble the global
figure
m_proj(proj{kp},'lon',110, 'lat',30','rad',90)
m_coast; m_grid;
case 3
% Azimuthal Equal-Area
% equal area but not conformal, also called lambert azimuthal
% equal-area projection
figure
m_proj(proj{kp},'lon',110, 'lat',30','rad',90)
m_coast; m_grid;
case 4
% Azimuthal Equidistant
% neither equal nor conformal,
% all distance from the centre point is true
figure
m_proj(proj{kp},'lon',110, 'lat',30','rad',30)
m_coast; m_grid;
case 5
% Gnomonic
% neither equal nor conformal
% all straight lines are great circle routes
% cause distortion at the edge of map
% max radii 20~30 at most
figure
m_proj(proj{kp},'lon',110, 'lat',30','rad',20)
m_coast; m_grid;
case 6
% Satellite
% perspective view of the earth
% viewpoint altitude is required
figure
m_proj(proj{kp},'lon',-20, 'lat',60','alt',2)
m_coast; m_grid;
% Cylindrical and Pseudo-cylindrical Projections
case 7
% Mercator
% conformal, straight lines are thumb lines
% 'lon',([min max]| center), in center means global map
% 'lat',[maxlat|[min max]), usually the same in both N and S latitude
figure
m_proj(proj{kp},'lon',-20, 'lat',60)
m_coast; m_grid;
case 8
% Miller Cylindrical
% neither equal nor conformal
% looks nice for world maps
figure
m_proj(proj{kp},'lon',-20, 'lat',[-85,85])
m_coast; m_grid;
case 9
% Equidistant cylindrical
% neither equal nor conformal
% equally-spaced lat and lon lines
% often used for quick plotting
figure
m_proj(proj{kp},'lon',-20, 'lat',[-85,85])
m_coast; m_grid;
case 10
% Oblique Mercator
% conformal not equal-area, around an arbitrary great circle
% used for very short-wide or tall-thin map, i.e. long coast lines
% two specified point lie in the middle (vertical or horizontal
figure
m_proj(proj{kp},'lon',[130,100], 'lat',[20,30],'dir','horizontal','asp',0.5)
m_plot([130,100],[20,30],'marker','x','color','r')
m_gshhs_l; m_grid;
case 11
% Transverse Mercator
% special case of 10,
% only meridian of longitude acts as the great circle
% the meridian can be fixed by 'clo'
figure
m_proj(proj{kp},'lon',[110 130],'lat',[0 30],'clo',115,'rec','on')
m_gshhs_l; m_grid;
case 12
% Universal Transverse Mercator (UTM)
% special case of 10
% only for high-quality maps of small regions
% ellipsodial projection
% set 'ell' other than normal, 'rec','on',and omit m_grid
% grid will be shown in meters
figure
m_proj(proj{kp},'lon',[115,125], 'lat',[30,40],'ell','sphere','rec','on')
% m_plot([130,100],[20,30],'marker','x','color','r')
m_gshhs_i; m_grid;
case 13
% Sinusoidal
% latitude as straight lines
% meridians curve
% equal-area
figure
m_proj(proj{kp},'lon',[80,150], 'lat',[0,60],'rec','on')
m_coast('patch',[.9 .9 .9]);
m_grid('ytick',[0:10:60],'backcolor',[184 215 245]/255);
case 14
% Gall-Peters
% parallel latitude and meridians
% vertical scale distorted to preserve area
% useful for tropical areas
figure
m_proj(proj{kp},'lon',[-80,150], 'lat',[-20,15])
m_coast('patch',[.9 .9 .9]);
m_grid('ytick',[-60:10:60],'backcolor',[184 215 245]/255);
% Conic Projections
% mid-latitude areas of large east-west extent
case 15
% Albers Equal-Area Conic
% equal area, not conformal
% 'clo', as center longitude
% 'rec', on off
figure
m_proj(proj{kp},'lon',[0,180], 'lat',[20,60],'rec','on')
m_coast('patch',[.9 .9 .9]);
m_grid('ytick',[-60:10:60],'backcolor',[184 215 245]/255);
case 16
% Lambert Conformal Conic
% conformal, not equal-area
figure
m_proj(proj{kp},'lon',[0,180], 'lat',[20,60],'rec','on')
m_coast('patch',[.9 .9 .9]);
m_grid('ytick',[-60:10:60],'backcolor',[184 215 245]/255);
% Miscellaneous Global Projections
% <,'lon<gitude>',[min max]>
% <,'lat<itude>',[min max]>
% <,'clo<ngitude>',value>
% <,'rec<tbox>', ( 'on' | 'off' )>
case 17
% Hammer-Aitoff
% equal area
% curved meridians and parallels
figure
m_proj(proj{kp})
m_coast;m_grid('xaxislocation','middle');
case 18
% Mollweide
% Parallels are straight
% Also called the Elliptical or Homolographic Equal-Area Projection
figure
m_proj(proj{kp})
m_coast;m_grid('xaxislocation','middle');
case 19
figure
m_proj(proj{kp})
m_coast;m_grid;
end
title(name)
saveas(gcf,[name,'.png'])
end
% MP_AZIM Azimuthal projections
% This function should not be used directly; instead it is
% is accessed by various high-level functions named M_*.
% Stereographic - conformal
% Orthographic - neither conformal nor equal-area, but looks like globe
% with viewpoint at infinity.
% Az Equal-area - equal area, but not conformal (by Lambert)
% Az Equidistant - distance and direction from center are true
% Gnomonic - all great circles are straight lines.
% Satellite - a perspective view from a finite distance
% Cylindrical
% Mercator - conformal
% Miller - "looks" nice.
% Equidistant - basically plotting by lat/long, with distances stretched.
% Conic Projections
% Albers equal-area - has an equal-area property
% Lambert conformal - is conformal
% Azimuthal projections
% Azimuthal projections are those in which points on the globe are projected
% onto a flat tangent plane. Maps using these projections have the property
% that direction or azimuth from the center point to all other points is shown
% correctly. Great circle routes passing through the central point appear as
% straight lines (although great circles not passing through the central point
% may appear curved). These maps are usually drawn with circular boundaries.
% The following parameters are needed to define an azimuthal projection:
% <,'lon<gitude>',center_long>
% <,'lat<itude>', center_lat>
% These parameters define the center point of the map. Maps are aligned so
% that the specified longitude is vertical at the map center, with its
% northern end at the top (but see option rotangle below).
% <,'rad<ius>', ( degrees | [longitude latitude] )>
% This defines the extent of the map. Either an angular distance in degrees
% can be given (e.g. 90 for a hemisphere), or the coordinates of a point on
% the boundary can be specified.
% <,'rec<tbox>', ( 'on' | 'off' | 'circle' )>
% The default is to enclose the map in a circular boundary (chosen using
% either of the latter two options), but a rectangular one can also be
% specified. However, rectangular maps are usually better drawn using a
% cylindrical or conic projection of some sort.
% <,'rot<angle>', degrees CCW>
% 1 Stereographic
% The stereographic projection is conformal, but not equal-area. This
% projection is often used for polar regions.
% 2 Orthographic
% This projection is neither equal-area nor conformal, but resembles a
% perspective view of the globe.
% 3 Azimuthal Equal-Area
% Sometimes called the Lambert azimuthal equal-area projection, this mapping
% is equal-area but not conformal.
% 4 Azimuthal Equidistant
% This projection is neither equal-area nor conformal, but all distances and
% directions from the central point are true.
% 5 Gnomonic
% This projection is neither equal-area nor conformal, but all straight lines
% on the map (not just those through the center) are great circle routes.
% There is, however, a great degree of distortion at the edges of the map,
% so maximum radii should be kept fairly small - 20 or 30 degrees at most.
% 6 Satellite
% This is a perspective view of the earth, as seen by a satellite at a
% specified altitude. Instead of specifying a radius for the map, the
% viewpoint altitude is specified:
%
% Cylindrical and Pseudo-cylindrical Projections
% Cylindrical projections are formed by projecting points onto a plane wrapped around the globe, touching only along some great circle. These are very useful projections for showing regions of great lateral extent, and are also commonly used for global maps of mid-latitude regions only. Also included here are two pseudo-cylindrical projections, the sinusoidal and Gall-Peters, which have some similarities to the cylindrical projections (see below).
% These maps are usually drawn with rectangular boundaries (with the exception of the sinusoidal and sometimes the transverse mercator).
%
%
% 7 Mercator
% This is a conformal map, based on a tangent cylinder wrapped around the
% equator. Straight lines on this projection are rhumb lines (i.e. the
% track followed by a course of constant bearing). The following properties affect this projection:
% <,'lon<gitude>',( [min max] | center)>
% Either longitude limits can be set, or a central longitude defined
% implying a global map.
% <,'lat<itude>', ( maxlat | [min max])>
% Latitude limits are most usually the same in both N and S latitude,
% and can be specified with a single value, but (if desired) unequal
% limits can also be used.
% 8 Miller Cylindrical
% This projection is neither equal-area nor conformal, but "looks nice"
% for world maps. Properties are the same as for the Mercator, above.
% 9 Equidistant cylindrical
% This projection is neither equal-area nor conformal. It consists of
% equally-spaced latitude and longitude lines, and is very often used for
% quick plotting of data. It is included here simply so that such maps
% can take advantage of the grid generation routines. Also known as the
% Plate Carree. Properties are the same as for the Mercator, above.
% 10 Oblique Mercator
% The oblique mercator arises when the great circle of tangency is
% arbitrary. This is a useful projection for, e.g., long coastlines or
% other awkwardly shaped or aligned regions. It is conformal but not
% equal area. The following properties govern this projection:
% <,'lon<gitude>',[ G1 G2 ]>
% <,'lat<itude>', [ L1 L2 ]>
% Two points specify a great circle, and thus the limits of this map
% (it is assumed that the region near the shortest of the two arcs is
% desired). The 2 points (G1,L1) and (G2,L2) are thus at the center of
% either the top/bottom or left/right sides of the map (depending on the
% 'direction' property).
% <,'asp<ect>',value>
% This specifies the size of the map in the direction perpendicular to
% the great circle of tangency, as a proportion of the length shown. An
% aspect ratio of 1 results in a square map, smaller numbers result in
% skinnier maps. Aspect ratios >1 are possible, but not recommended.
% <,'dir<ection>',( 'horizontal' | 'vertical' )
% This specifies whether the great circle of tangency will be horizontal
% on the page (for making short wide maps), or vertical (for tall thin
% maps).
% 11 Transverse Mercator
% The Transverse Mercator is a special case of the oblique mercator when
% the great circle of tangency lies along a meridian of longitude, and
% is therefore conformal. It is often used for large-scale maps and
% charts. The following properties govern this projection:
% <,'lon<gitude>',[min max]>
% <,'lat<itude>',[min max]>
% These specify the limits of the map.
% <,'clo<ngitude>',value>
% Although it makes most sense in general to specify the central meridian
% as the meridian of tangency (this is the default), certain map
% classification systems (noteably UTM) use only a fixed set of central
% longitudes, which may not be in the map center.
% <,'rec<tbox>', ( 'on' | 'off' )>
% The map limits can either be based on latitude/longitude (the default),
% or the map boundaries can form an exact rectangle. The difference is
% small for large-scale maps. Note: Although this projection is similar
% to the Universal Transverse Mercator (UTM) projection, the latter is
% actually ellipsoidal in nature.
% 12 Universal Transverse Mercator (UTM)
% UTM maps are needed only for high-quality maps of small regions of the
% globe (less than a few degrees in longitude). This is an ellipsoidal
% projection. Options are similar to those of the Transverse Mercator,
% with the addition of
% <,'zon<e>', value 1-60>
% <,'hem<isphere>',value 0=N,1=S>
% These are computed automatically if not specified. The ellipsoid
% defaults to 'normal', a spherical earth of radius 1 unit, but other
% options can also be chosen using the following property:
% <,'ell<ipsoid>', ellipsoid>
% For a list of available ellipsoids try m_proj('set','utm').
% The big difference between UTM and all the other projections is that
% for ellipsoids other than 'normal' the projection coordinates are in
% meters of easting and northing. To take full advantage of this it
% is often useful to call m_proj with 'rectbox' set to 'on' and not
% to use the long/lat grid generated by m_grid (since the regular
% matlab grid will be in units of meters).
% 13 Sinusoidal
% This projection is usually called "pseudo-cylindrical" since parallels
% of latitude appear as straight lines, similar to their appearance in
% cylindrical projections tangent to the equator. However, meridians
% curve together in this projection in a sinusoidal way (hence the name),
% making this map equal-area.
% 14 Gall-Peters
% Parallels of latitude and meridians both appear as straight lines, but
% the vertical scale is distorted so that area is preserved. This is
% useful for tropical areas, but the distortion in polar areas is extreme.
% Conic Projections
%
% Conic projections result from projecting onto a cone wrapped around the
% sphere. The vertex of the cone lies on the rotational axis of the sphere.
% The cone is either tangent at a single latitude, or can intersect the
% sphere at two separated latitudes. It is a useful projection for
% mid-latitude areas of large east-west extent. The following properties
% affect these projections:
% <,'lon<gitude>',[min max]>
% <,'lat<itude>',[min max]>
% These specify the limits of the map.
% <,'clo<ngitude>',value>
% The central longitude appears as a vertical on the page. The default value
% is the mean longitude, although it may be set to any value (even one
% outside the limits).
% <,'par<allels>',[lat1 lat2]>
% The standard parallels can be specified. Either one or two parallels can
% be given, the default is a single parallel at the mean latitude
% <,'rec<tbox>', ( 'on' | 'off' )>
% The map limits can either be based on latitude/longitude (the default),
% or the map boundaries can form an exact rectangle which contain the given
% limits. Unless the region being mapped is small, it is best to leave this
% 'off' .
% The default is to use a spherical earth model for the mapping transformations.
% However, ellipsoidal coordinates can also be specified. This tends to be
% useful only for doing coordinate transformations (e.g., if a particular
% gridded database in in this kind of projection, and you want to find
% lat/long data), since the difference would be impossible to see by eye on
% a plot. The particular ellipsoid used can be chosen using the following
% property:
% <,'ell<ipsoid>', ellipsoid>
% For a list of available ellipsoids try m_proj('set','albers').
%
% 15 Albers Equal-Area Conic
% This projection is equal-area, but not conformal
% 16 Lambert Conformal Conic
% This projection is conformal, but not equal-area.
%
% Miscellaneous global projections
%
% There are a number of projections which don't really fit into any of the
% above categories. Mostly these are global projections (i.e. they show the
% whole world), and they have been designed to be "pleasing to the eye".
% I'm not sure what use they are in general, but they make nice logos!
%
% 17 Hammer-Aitoff
% An equal-area projection with curved meridians and parallels.
% 18 Mollweide
% Also called the Elliptical or Homolographic Equal-Area Projection.
% Parallels are straight (and parallel) in this projection. Note that
% example 4 shows a rather sophisticated use designed to reduce
% distortion, a more standard map can be made using
% m_proj('mollweide');m_coast('patch','r');m_grid('xaxislocation','middle');
% 19 Robinson
% Not equal-area OR conformal, but supposedly "pleasing to the eye".
