MAPPING BASICS 101 DIY PRECISION AGRICULTURE

Transcription

1 MAPPING BASICS 101 DI PRECISION AGRICULTURE

2 WHAT IS THE PURPOSE OF A MAP? Maps are a diagrammatic representation of an area of land. They provide the ability to communicate the location of areas of interest. ou may be interested in visiting a location or marking out a poor yielding portion of a paddock. Sharing a location, defining its characteristics and being able to locate it on the ground all require a map.

3 DATUMS,GLOBAL POSITIONING SSTEMS (GPS) & COORDINATE SSTEMS So how do we create a map? The earth is a curved object, when creating a map the information of a curved object is transferred onto a flat surface such as paper or your computer screen. Changing a curved surface to a flat map requires the use of datums. Datums are the mathematical model that creates a coordinate system (latitude and longitude) based on a set of reference locations that describes your position relative to the true shape of the earth. From this we can then use the coordinate systems to create the area of the earth on a flat surface, or a map. There are many different datums using different mathematical models to create coordinate systems. All datums produce distortions, as the earth has an inconsistent surface and not a perfect sphere. Problems often occur when data is created in one coordinate system and then projected into another. When using a global positioning systems (GPS), machinery guidance or when making a map, the datum and coordinate system must be consistent. In agriculture we mostly use World Geodetic System 84 (WGS84) as it is a world generic system. As for the coordinate system we generally work in latitude and longitude in the format of decimal degrees, purely because most of the agricultural machinery works in this format. Below lists some of the other latitude and longitude co-ordinate systems: Decimal Degrees Degrees, Minutes, Seconds Degrees, Decimal Minutes Universal Transverse Mercator Map Grid of Australia

4 CREATING DATA - VECTOR & RASTER In Geographic Information Systems (GIS Mapping), the two main structures used to create information are vector and raster data. Vector data is created by a series of x,y coordinates made up of points, lines and polygons. Raster data is created by rows and columns that produce a grid. Each grid square has a colour code depending on a data value allowing you to display information. The raster view of the world WA Wheatbelt areas of interest The vector view of the world POINTS: PUB A LINES B AREAS: SALT LAKES & FARMS LINES: ROADS SURFACE ELEVATION

5 VECTOR DATA - POINTS, LINES & POLGONS Vector objects are all produced by x,y coordinates. Points = single x,y. Lines = multiple x,y points joined. Polygons = multiple x,y points joined and enclosed. POINTS (Latitude, longitude) LINES A POLGONS B A point is a single location, identified by a latitude and longitude. Attached to this location can be any number of attributes, such as yield, moisture, ph, etc. In a cropping situation points are single objects such as a power pole, stake in the ground or a yield data point which has a single location defined by its coordinate system that ties it to the earth. ield data is just the header continuously creating points, with a latitude, longitude and the attribute of yield attached, along with many other attributes such as moisture, speed, fuel consumption, etc. For example the table below shows some yield data in its raw format. Latitude Longitude ield Mass Speed Moisture (Dry) Lines are two or more points connected by a string. So each point has a latitude and longitude which then defines the lines location on the earth. An AB guidance line uses point A (latitude, longitude) and point B (latitude, longitude) to position the tractor on the earth. Roads on maps are drawn using lines created by multiple points showing the transition of a path. Polygons are enclosed shapes created by a series of points which are connected with lines, all georeferenced to the ground via the points. This paddock boundary shows a simple polygon, where the outside has been defined by a series of points and then enclosed. A yield map is a more complex set of polygons, created using thousands of yield data points which are then interpolated to create multiple polygons within a paddock boundary. Each polygon is colour coded to a selected yield range. For example, here is a yield map that has grouped the yield results into three ranges; red, yellow and green, to display the different yielding regions within the paddock.

6 FILE TPES Once you create mapping data sets, how do you store them? Points, lines and polygons are the building blocks of mapping, however they can be dressed up in all sorts of file types. It is best to just think of the file type as the clothing. Simple mapping programs where the mapping file is created will usually determine what file type will be used. However, in the more advanced mapping programs you will generally be able to choose your file type. This table displays some of the general file types used in mapping, how they are expressed and where you would typically find them. File Type Expression Description Where is it used? Examples Text files.csv/.txt A file created using text. Information is separated using spaces or commas. Shapefiles.shp This is the mapping industry standard. Each file can be made up of between 3 to 5 different files. Google Earth Raster/ Image/ Geotiff.kml/.kmz.tif Kml or keyhole mark-up language (z is zipped) is what Google created for Google earth. Image files are created by georeferencing a grid to the ground. Each grid has a number assigned to it that then codes it for a colour; the same way televisions display images. Excel, Word Mapping Platforms, ESRI ArcMap, Ag Machinery Google Earth only, Some apps Screens Soil test results Google earth pro Google earth maps Computer, Television, NDVI, Prescription map

7 DATA CARD MANAGEMENT Storing multiple years of yield data is critical for precision agricultural (PA) mapping and to prevent data loss and corruption there is one simple rule: BACK UP, BACK UP, BACK UP! ield data is a map of a paddocks grain yield in specific locations, essentially mapping the income a crop produces across the landscape. ield data is highly variable. This can be due to a multitude of factors. For this reason, you often need several years of yield data to make confident management decisions. By storing your yield data after every harvest, you will begin to accumulate a library of information which represents different years and their associated variables. This will then allow you to correlate specific years to their agronomy problems. Multiple years of yield data with similar agronomy problems will provide a better idea of the zones for specific issues. For example a dry spring may clearly demonstrate low yielding soils due to low plant available water capacity (PAWC), while the next year may be very wet and show what soils are prone to waterlogging.

8 HOW TO BACK UP OUR MACHINES DATA CARD: 1 When 2 3 At 4 Plug collecting yield data with a USB/data card, older machines often require a small capacity (<4GB) good quality USB. This storage device (USB/card) collects the information created from the machinery monitor and the GPS receiver. This is generally in the form of point data (latitude, longitude and attributes = yield data, speed, moisture, etc ). Depending on the data logging frequency, you will have many thousands of data points within a paddock. the end of harvest, when powered off, remove the USB/card from the monitor. It is a good idea to check after the first day/paddock that data is recording correctly the USB/card into computer and open it in Windows Explorer to see the yield data files. Depending on the make of your harvester the folder will have a different name attached to it. File type examples Machinery File Type Things to consider Case IH.cn1 or.cnh John Deere New Holland Class Massey Ferguson, Trimble & Topcon 5 Right 6 Create 7 Name 8 Right RCD folder RCD folder on older GS2 screens. New file name is GS3_2630 on GS3 screens..cn1 or.cnh.dat or.ml Task data folder.ml Task data folder click the folder and choose copy. Because John Deere creates a whole folder named RCD be careful to always change the title of the folder to Harvest and the year to create a distinguishable file if you just copy and paste the new RCD folder, it will overwrite the old due to having the exact same name. Must be aware that yield data will be inside a folder called task data folder, if you copy and paste this folder into the same place as last year it will overwrite due to having the exact same name. a folder on the desktop by right clicking anywhere on the desktop screen and choosing new then folder. the new folder = EAR & Harvest for example 2007 Harvest data cards. click on the newly created folder and choose paste this will import all the yield data into the folder. Also copy the data card to an external hard drive so you have a copy independent from your computer. Now you have two copies of your data in separate locations. After this, go back to the USB icon in My Computer, right click and chose format. Formatting the USB will erase everything from the USB and return the settings back to what they were when it was new. Eject the USB card by right clicking the icon and choosing eject. If you are unsure of the backup process simply purchase another USB/card storage device. Proprietary storage USB s are not required, a generic USB is sufficient.