Creating a time series of rasters.

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09-12-2013 02:51 PM
ScottBarron
New Contributor III
Hi,
I have a number of rasters showing precipitation values for different months. I'd like to create a time series to visually show how this changes over time. I've tried googling for answers on how to do this, but have come up short. Any advice?
Thanks,
Scott
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MichaelVolz
Esteemed Contributor
How about a raster mosaic dataset where you enable the time feature?  You can load multipule raster mosaic datasets into another raster mosaic dataset that you could consider a composite raster mosaic dataset.  Then you can add a new field to this composite mosaic dataset with a meaningful name such as YEAR.  Then populate this field with the year of each raster mosaic dataset.  Then set the Time properties of the composite raster mosaic dataset using the field you just added.  You would then need to open the Time Slider Window which would only be enabled if the selected layer has a time property enabled.  Once this time slider window is also properly enabled you can slide the bar to see the rasters change as you move from year to year.  Please note that if there are gaps in your data (You do not have rasters for each year), no raster will show up at that interval(s). I believe this was new functionality to ArcGIS v10.0.

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curtvprice
MVP Esteemed Contributor
I have a number of rasters showing precipitation values for different months. I'd like to create a time series to visually show how this changes over time.


The way you do this in ArcGIS is by loading your time series of rasters into a raster catalog.


'>Desktop Help 10.0: Displaying a time series raster catalog


UPDATE:
Michael Volz rightly suggested mosaic datasets, which are the better way to do it in 10.x.


'>Desktop 10.2 help: Time in a mosaic dataset
(not much change since 10.0)
MichaelVolz
Esteemed Contributor
How about a raster mosaic dataset where you enable the time feature?  You can load multipule raster mosaic datasets into another raster mosaic dataset that you could consider a composite raster mosaic dataset.  Then you can add a new field to this composite mosaic dataset with a meaningful name such as YEAR.  Then populate this field with the year of each raster mosaic dataset.  Then set the Time properties of the composite raster mosaic dataset using the field you just added.  You would then need to open the Time Slider Window which would only be enabled if the selected layer has a time property enabled.  Once this time slider window is also properly enabled you can slide the bar to see the rasters change as you move from year to year.  Please note that if there are gaps in your data (You do not have rasters for each year), no raster will show up at that interval(s). I believe this was new functionality to ArcGIS v10.0.
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ScottBarron
New Contributor III
I'm trying both of the methods above but I'm still having trouble, maybe I'm just not understanding something. I think part of the problem is that my rasters don't have a column for year or date because they don't have attribute tables. In order to generate attribute tables I would have to change all the values to integer, and that wouldn't be good.

I'm working with a bunch of individual rasters with the same extents that show precipitation values across the globe, if that helps at all.

Thanks,
Scott
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MichaelVolz
Esteemed Contributor
Scott:

You do not add the YEAR (or whatever time frame you call it) field to the rasters themselves.  You add this field to the raster mosaic dataset that is linked to the rasters via some pointer to their file location.
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ScottBarron
New Contributor III
Ah ha! The mosaic dataset strategy worked! Thank you so much. One more related question, is there an easy way to keep my file names when adding the rasters to the mosaic dataset? It changes my names to F1...

Thanks,
-Scott
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curtvprice
MVP Esteemed Contributor
  One more related question, is there an easy way to keep my file names when adding the rasters to the mosaic dataset? It changes my names to F1...


I think you don't want to copy your data, you want to create a referenced mosaic dataset instead. If your datasets are large, this is very handy because you don't need to store it twice to access it as a mosaic -- and you can continue access each tile as a raster if you need to.

Desktop Help 10.2: What is a mosaic dataset?
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ScottBarron
New Contributor III
The mosaic data vs referenced mosaic dataset don't appear to be different at all after I created a referenced mosaic dataset from my regular one. Also, I'm still confused about how to change the label for my mosaic dataset. All of my raster files are labeled along the lines of "012013" for January of 2013, however the time series reads this as the year "0001". I'm still stuck on how to deal with this problem.

Thanks,
Scott
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curtvprice
MVP Esteemed Contributor
Also, I'm still confused about how to change the label for my mosaic dataset. All of my raster files are labeled along the lines of "012013" for January of 2013, however the time series reads this as the year "0001".


The raster mosaic has a table that has one row for each raster. Add a field of type DateTime and use the Calculate Field to convert the label field ("012013" to time). A VBScript expression in Calculate Field will convert date strings of the type "m/d/yyyy" to datetime for you, so you can use this expression:

Left([LABEL],2) & "/01/" & Mid([LABEL],3,4)



'>Esri KB 31877 HowTo: Convert a text field to a date field
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ScottBarron
New Contributor III
I assumed there would be something like that, but I can't find a table anywhere. I've tried right clicking on the mosaic dataset itself, as well as the "image" subsection.
-Scott
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