MATLAB Map Toolbox Learning Summary (i) from the map projection

MATLAB Map Toolbox Learning Summary (i) from the map projection

Objective

In this semester's map projection class, Li Lianying suggested that we use MATLAB to complete our weekly assignments. From the sophomore semester began to contact with MATLAB Learning Mathematical Computing and geographic data processing I, naturally will not let go of this opportunity, every week to find a little time to study a bit, the work easier to take care of. However, due to the online related tutorials, less information, in the inclusion of a variety of professional vocabulary at the same time, there is no Chinese translation, but also makes people feel headache. Here you want to summarize the relevant functions to help others who need to use the toolbox. As a student, I am only exposed to the fur, there will inevitably be some mistakes, I hope to see the people can point out, thank you.

PS: This article is based on the MATLAB r2014a version.

1 Work Case: Map projection Job 5-7

In the assignment 5, 6, 7, teacher Li separately asked us in MATLAB to draw the positive axis, the horizontal axis, the direction of the oblique shaft, cylindrical, conic projection (parameter custom), consult the MATLAB help, on the basis of the completion of the work. Take the isometric horizontal cylindrical projection as an example, as shown in the source code and the effect:

Landareas = Shaperead (' landareas.shp ', ' usegeocoords ', true);

Axesm (' Mercator ', ' Frame ', ' on ', ' grids ', ' on ', ' origin ', [0 120 0]);

Geoshow (Landareas, ' Facecolor ', [1 1.5], ' Edgecolor ', [. 6.6.6]);

Tissot

Next I will explain in detail the meanings and effects of each function and its parameters.

2 Classification of Map projections:

(1) MATLAB supports a variety of map projections, to see the specific support for the only need to type maps on the command line, you can get all the map projection types in MATLAB classification properties (cone, cylinder, azimuth projection, etc.), the name and the abbreviation used in MATLAB. Such as:

(2) The following is my own translation of the partial projection type in English translation comparison table.

3 Usage of Shaperead

Shaperead is used to read data from a Shapefile file and store it.

(1) Basic usage: Shpaeread (filename,name,value)

where filename refers to a file name, this key must be set, followed by multiple settings. It generates a structure that includes data such as geometry geometry, BoundingBox range, and x, Y coordinate values.

(2) Common settings

1) BoundingBox: is a 2*2 array that restricts the reading of the range of file features, only the features within that range can be selected.

2) Attributes: Reads the property settings followed by a string array, which is the property to be read. When this property is set, only selected attributes in the Shapefile file can be read.

3) Usegeocoords: You can choose to be true or False (default), that is, whether to use a geographic structure (geostruts). If the data has already been projected, select false, and if it has not yet been projected, you can select True to generate the projection.

4 usage of AXESM

AXESM is one of the most important and commonly used functions in the Map Toolbox to define the coordinate system of the map and set the properties of the map. The type of map projection can also be set and adjusted inside.

(1) Basic usage: AXESM (projid,propertyname,propertyvalue)

Where ProjId refers to the short name of the projection type, which must be set, followed by a number of attributes, including the property name and the property value. Attributes are divided into four categories: controlling the properties of the map projection, controlling the properties of the frame, controlling the properties of the grid, and controlling the properties of the axis labels. Here are some common properties. Alternatively, you can manually adjust some of the parameters by typing axesm directly on the command line.

(2) Common properties:

1) AngleUnits: Includes degrees (default) degrees and radians radians two properties, which define the units of the angle.

2) Maplatlimit[southern_limit Northern_limit] and Maplonlimit[western_limit Eastern_limit]: Defines the range of longitude and latitude, respectively

3) Origin[latitude Longitude Orientation]: Defines the center area of the map. The latitude and longitude of the input will be the center of the map. The last parameter, orientation, sets the angle of the map rotation.

4) Frame: Includes both on and off (default) two properties. You can define whether the border of the map is displayed.

5) Grid: Includes both on and off (default) two properties. Whether the map grid can be displayed.

5 Usage of Geoshow

Geoshow is a function for displaying map data, which is important for most maps to display using this function. Because of the variety of methods used, here are just a few of the uses that are relevant to the beginning of this article.

(1) Basic usage:

1) geoshow (lat,lon) direct input latitude and longitude, will be centered on this latitude and longitude, to generate a small map.

2) geoshow (filename) Enter the map file name directly, generate the map

3) Geoshow (_,name,value,) enter the relevant properties and set the parameters to generate the desired map.

(2) Common properties:

1) Facecolor: Defines the color of the map surface, requires three parameters and is between 0 and 1.

2) Edgecolor: Defines the color of the coastline boundary, with the same parameter values.

6 usage of Tissot

The Tissot is used to display the deformed ellipse.

(1) Basic usage:

1) Tissot can automatically display the deformed ellipse, and the minimum ellipse size is one-tenth of the display range.

2) Tissot (RADIUS) where radius is the size of the smallest ellipse.

3) Tissot (LineStyle) wherein the linestyle is elliptic linear.

4) Tissot (Linestyle,propertyname,propertyvalue) can set other properties about the line.

Today about the Matlab map projection of the relevant knowledge to introduce so much, see Help is the most important, I just picked out the relevant individual properties, but Matlab is really powerful, should be good use! Next time you're ready to talk about the problem of the great circle and the constant line path generation.

Tian Jing, the Hermit

2016.4.18

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MATLAB Map Toolbox Learning Summary (i) from the map projection