ArcGis How To

Question 1

what does an .mxd file save?

Answer 1

Saves the list of layers you have, the current displays (maps etc) and pointers to your data. The .mxd file does not include your data sets - just the location
File → Need to go into map documents properties → store relative pathnames to data source

Question 2

select by attribute

Answer 2

In box of all attributes associated with each value - double click on the attribute you want, then “get unique values”
If you want to use this permanently need to export as a new shapefile - but select “selected features” under export options and save as a shapefile
Then import as a new layer and unselect the old selection highlight

Question 3

how to find the coordinate system/projection info for data frame

Answer 3

View → data frame properties → coordinate system tab → in box labelled current coordinate system → can search for other systems and change them here
For a basic latitude and longitude geographic coordinate system: World geographic system (WGS) 1984 (under world folder)

Question 4

how to find a coordinate system/projection information for a layer

Answer 4

Double click on layer in table of contents to open the layer properties → source tab → in box under data source

Question 5

quantities symbology

Answer 5

Open up layer properties → symbology→ quantities→ graduate symbols → choose classification method to set cutoffs → tidy up labels for the cutoff → select symbols and colours

Question 6

attribute table functions

Answer 6

Select by attribute
Sorting - right click on the column heading for sorting options (ascending, descending)
Statistics - right click on the column heading for a numeric field.
Field calculator (for prevalence)
Calculate geometry

Question 7

eliminating extra decimals and commas

Answer 7

In properties/symbology click on label section heading and select format labels→ under option for number of significant digits change the field to one or two (no more unless dealing with values less than 1)

Question 8

break apart a legend

Answer 8

Caution: once done this the legend will no longer automatically update
R click on legend → convert to graphics → right click on all the selected pieces of the legend again → ungroup —> repeat
Now can modify and move all the pieces of the legend around

Question 9

To add GPS coordinates

Answer 9

Go to table that has been importanted and right click and select “display XY data”change X field to “point X” and y field to point y
Make sure it is set to the right projection
To make plotted points permanent it has to be exported as a shapefile and re-imported
Make sure to turn off the temporary layer

Question 10

How to create new shapefiles

Answer 10

Open up ArcCatalog (at the side of screen). Select folder with raw data and rick click > new > shapefile
Select whether it is a point, polygon, polyline etc. and give it a coordinate system and name it
Make sure the new shapefiles are in the table of contents, if not drag into it from the ArcCatalog

Question 11

Digitizing

Answer 11

Need to make sure attribute table has matching fields for ids
Attribute table → table options → add field
Make editor toolbar visible: view > toolbar > edit. Select :”start editing”under source select the folder directory where you created shapefiles
Click on create features from editor toolbar and make sure to select the right field from the create features directory
As make new points make sure to update the attribute table with the right id
If need to move a point placed use the little black arrow next to the editor drop down menu

Question 12

Table join

Answer 12

Have to be outside of an edit session
Go to layer and right click > joins and relates > join > table join > select “join attributes from a table:, the field you want joins, the table you want the information added from → once completed remember to export and re-import as a shapefile

Question 13

How to calculate prevalence

Answer 13

Attribute table: Add a new field, name it and select double type
In attribute table select those house with at least 1 malaria case
On the new field right click and select field calculator
CASES / PEOPLE * 100

Question 14

How to find mean centre, median centre, directional distribution

Answer 14

Toolbox icon → spatial statistics → measuring geographic distributions
Input: the shapefile with information
Output: what you want it named
Weight field is optional - for the number of people, cases or prevalence that you would liked to consider
For directional distribution have to select the ellipse size

Question 15

To find nearest location

Answer 15

Make sure the reference point have X, Y coordinates and are in the same projection and are all merged as 1 shapefile
To merge go to geoprocessing > merge > input the data sets and export
Do a spatial join with the closest distance option starting with the thing you are measuring distance to (e,g, households) and specify the reference point (e.g. boreholes) to join
In spatial join select the option “each point will be given all the attributes of the line that is closest to it and a distance field showing how close that line is”
Export and re-import

Question 16

Buffering

Answer 16

Geoprocessing > buffer > select input file > name output > put the distance amount and unit > to have a dissolved buffer select dissolve under dissolve type, if undissolved select none

Question 17

Creating an address locator

Answer 17

ArcCatalog > right click on file where you have address file stored > new > address locator
Under locator style choose US Address Dual Ranges > select reference data
Select file name for locator

Question 18

Geocoding addresses in a table

Answer 18

If you have a table that contains address information can geocode multiple addresses simultaneously
Import table > right click on select geocode addresses
Select the address locator (may have to create one and import)
Make sure field for address input fields are
Street: address, city: city, state: state or blank, ZIP code: Zip
Name output file and save as shapefile
Get ArcGIS add the X, Y Coordinates to attribute table for output file: click geocoding options and select check X,Y coordinates in the box
Click ok and let the geocoding process
Table will appear with matched, tied and unmatched - can close or rematch (want around 80% match)
Make sure you export final geocoding result for backup

Question 19

rematching addresses

Answer 19

To see unmatched select unmatched from drop down menu
Look up under address column the addresses with lot, apt, suite numbers etc that can be removed and look up addresses for PO Boxes by googling the id
Once have a new address type that into section below. If a new option comes up select if, if not them the address has to be exclude

Question 20

which layer to select first in a join

Answer 20

Start with the layer where you want the data to go to and specific the data file you would like the data from

Question 21

clipping

Answer 21

Geoprocessing > clip > input the feature to be clipped > clip features: feature used to clip (cookie cutter) > name output and export as a feature class

Question 22

spatial join

Answer 22

Right click on layer > joins and relates > join > spatial join > select join data from another layer based on spatial location > choose the data file > select “sum” and anything else you want > name output and export as a shp

Question 23

labelling

Answer 23

Layer properties > labels tab > select label features in this layer > select label field
To label with name + number of cases: sector = label field, expression: sector & “,” & cases
Add halo under edit symbol
Convert to annotation to be able to move labels around: right click > convert labels to annotation > change to in the map

Question 24

create a geodatabase

Answer 24

`Right click on folder > new > personal database > import data by right clicking on geodatabase (suffix mdb)