# اسلاید پاورپوینت: برآمدگی (projection) ، نقشه (map) و وزنه (scale)…

### عناوین اصلی استخراج شده از این فایل پاورپوینت

● Today’s class
● Need for Map Projections
● Types of map projections
● Projection by characteristics
● Scale characteristics
● Large/small scale map
● Projection type by surface
● General characteristics
● Plane projection maps
● Conical Projection
● Conical Projections
● Cylindrical Projections
● UTM coordinates
● Example of using UTM coordinates
● Notes that go with previous figure
● UTM coordinates
● Map Projection resources
● North America under different projections
● Summary

 نوع زبان : انگلیسی حجم : ۰٫۲ مگا بایت نوع فایل : اسلاید پاورپوینت تعداد اسلایدها: ۲۱ صفحه زمان استخراج مطلب : ۲۰۱۸/۱۱/۰۲ ۰۸:۱۴:۱۴ پسوند فایل : ppt

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این مطلب در تاریخ ۲۰۱۸/۱۱/۰۲ ۰۸:۱۴:۱۴ به صورت خودکار استخراج شده است. در صورت اعلام عدم رضایت تهیه کننده ی آن، طبق قوانین سایت از روی وب گاه حذف خواهد شد. همچنین این مطلب برگرفته از وب سایت زیر است و مسئولیت انتشار آن با منبع اصلی است.

### بخشی از محتوای متن استخراج شده از این فایل ppt

۱۲.۲۱۵ modern navigation thomas herring tah@mit.edu http geoweb.mit.edu ~tah ۱۲.۲۱۵ ۱۲.۲۱۵ lec ۱۱ today’s class map projections why projections are needed types of map projections classification by type of projection classification by characteristics of projection mathematics of map projections ۱۲.۲۱۵ lec ۱۱ need for map projections basic need is because the earth’s surface is curved and so it is not possible to represent on a flat surface with out some distortions flat surfaces were needed so that people could carry maps with them still a major use with gps maps are now often represented in a computer in ۳ d form or as ellipsoidal coordinates thus minimizing the distortion the amount of distortion depends on the area to be represented over small areas the earth is nearly flat . ۱۲.۲۱۵ lec ۱۱ types of map projections map projections are classified either by way the projection is made and the surface onto which it is projected or by the characteristics of the resultant projected maps. some projection surfaces are planes cones and cylinders each of these surfaces can be un wrapped into a flat surface some map projections are purely mathematical so that they can minimize distortions. we will deal mathematically with only projection from a spherical body. most accurate map projections are projections from an ellipsoidal body. ۱۲.۲۱۵ lec ۱۱ projection by characteristics the general characteristics of map projections are given by conformality when the scale of a map at any point on the map is the same in any direction the projection is conformal. meridians lines of longitude and parallels lines of latitude intersect at right angles. shape is preserved locally on conformal maps. distance a map is equidistant when it portrays distances from the center of the projection to any other place on the map. direction a map preserves direction when azimuths angles from a point on a line to another point are portrayed correctly in all directions. area when a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the earth that they represent the map is an equal area map. ۱۲.۲۱۵ lec ۱۱ scale characteristics scale scale is the relationship between a distance portrayed on a map and the same distance on the earth. a large scale map shows a small area with a large amount of detail eg. ۱ ۲۵ a small scale map shows a large area with a small amount of detail eg. ۱ ۵ the interpretation of the scale is ۱ ۲۵ is ۱ unit on the map represents ۲۵ units on the earth on many maps the scale changes across the map. usually the scale is shown graphically somewhere on the map and if the scale varies across the map the scale should indicate where it is applicable and the changes in scale across the map. ۱۲.۲۱۵ lec ۱۱ large small scale map large scale small scale note scale bar in lower left hand corner source http www.mapblast.com ۱۲.۲۱۵ lec ۱۱ projection type by surface projections are often referred to by the type of surface that the projection is made on to. the three main surfaces are plane often referred to a azimuthal projections cylindrical mercator is probably the most famous conic projection the characteristics of the map are set by how the surface contacts the earth e.g. a plane may be tangential to the surface or it may cut through the earth at some depth. ۱۲.۲۱۵ lec ۱۱ general characteristics all projections can be written in a form that allows plane coordinates x and y to be written as functions of f and l x f f l and y g f l . the exact forms of the functions f and g depend on the projection. for the geometric projections from a sphere these can be written as simple trigonometric functions as shown in the next few slides. more complicated projections can involve more complicated and sometime approximate formulas especially when ellipsoidal coordinates are projected such as the universal transverse mercator utm projection which is used for many us maps on many maps utm coordinates are given also called grid coordinates and gps receivers can normally be set to output and interpret these types of coordinates. ۱۲.۲۱۵ lec ۱۱ plane projection maps ۱۲.۲۱۵ lec ۱۱ conical projection the equations to solve the conical projection will be set as a homework exercise. in a conical projection points are projected radially onto the cone. the cone is then cut and unwrapped to form the projection. in the case shown the cone’s dimensions are set by specifying the co latitude of the tangent point of the cone qt . the distance around this part of the cone is set equal to the distance around the small circle on the earth. this allows the relationship between longitude and the angle around the cut cone b to be determined. ۱۲.۲۱۵ lec ۱۱ conical projections ۱۲.۲۱۵ lec ۱۱ cylindrical projections ۱۲.۲۱۵ lec ۱۱ utm coordinates the universal transverse mercator utm projection is most commonly used in the us and many other mid latitude to equatorial countries this is an ellipsoidal projection that divides the world into numbered zones in longitude. for the us these zones are ۱۲.۲۱۵ lec ۱۱ utm coordinates within each of the zones the latitude and longitude difference from the central meridian is used to compute the utm coordinates. these coordinates are given as northing and easting. the east coordinates have ۵ added so that they are not negative west of the central meridian ۱۲.۲۱۵ lec ۱۱ example of using utm coordinates ۱۲.۲۱۵ lec ۱۱ notes that go with previous figure utm coordinate maps usually have notes that describe the projection in more detail details given on datum nad ۲۷ in this case more details at http www.maptools.com usingutm ۱۲.۲۱۵ lec ۱۱ utm coordinates software for converting latitude and longitude to utm coordinates is available at ftp ftp.ngs.noaa.gov pub pcsoft utms this software available as pc executable and as …

### کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: برآمدگی (projection), نقشه (map), وزنه (scale), هم مرتبه (coordinate), رویه (surface), سطح (area), سکنه زمین (earth),

این فایل پاورپوینت شامل ۲۱  اسلاید و به زبان انگلیسی و حجم آن ۰٫۲ مگا بایت است. نوع قالب فایل ppt بوده که با این لینک قابل دانلود است. این مطلب برگرفته از سایت زیر است و مسئولیت انتشار آن با منبع اصلی می باشد که در تاریخ ۲۰۱۸/۱۱/۰۲ ۰۸:۱۴:۱۴ استخراج شده است.

http://www-gpsg.mit.edu/~tah/12.215/12.215.Lec11.ppt

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