Show Me the Data!


The Digital Coast Data Access Viewer, lovingly referred to as DAV, gets thousands of data requests each month.  DAV does a great job distributing these data requests across multiple servers so that you get data lickety-split.   I’d say this is the case 99% of time.  But why just 99% of the time?  DAV should be able to process ALL of the requests quickly, right?  And if not, then at least in a timely manner, shouldn’t he?  Well…  it is not entirely DAV’s fault when you don’t get data, and in some cases, DAV is just an innocent bystander.  What you may not know is that when DAV runs into a problem, he raises a red flag (in the form of an email), asking  for help.  A small bunch of people put on their DAV thinking hats and run to his rescue.  Here are some of the most common issues that throw DAV into a tizzy.

Wrong email addresses are arguably one of the most common issues that give DAV trouble.  It is the most basic piece of information that is entered in the checkout process but yet is the most important.  DAV tries to send an email to let you know that the data has been extracted, transformed, zipped, and ready for downloaded but he is not always successful.   Although I talk about DAV as if he is a person, he isn’t.  DAV is a computer system.  He literally does what you tell him to do.  So, if you enter your email address as imarockstar@otmail.com,  then that is where he is going to send the data notification email.  He doesn’t know that you meant to type hotmail instead of otmail.  DAV may not be able to figure that out, but he is smart enough to know that there is a problem and he even knows that the email address is the culprit. So, moral of this story, check and double check your email address.  It could be the reason why you never received your data.

Sometimes, DAV isn’t to blame when you don’t get your data.   Not to point fingers, but I’m gonna have to call out your spam filter.  I’m not saying to change your filter settings because no one wants spam.  But there is always the chance that something important, like DAVs email, got filtered into the spam folder.  You should check this folder if you haven’t received anything from Digital Coast.  Alternatively, the email that DAV sends may be getting blocked by your office.  Since DAV sends an email from a generic account, it is possible that your office labels it as stranger-danger and rejects the email before you even see it.  It is highly likely that you will eventually receive the data notification email but it may take some time for DAV to ask a real person to send the email on his behalf.

Another common reason for not receiving data lickety-split is because there isn’t data available in the area of interest that you selected.  This problem is not restricted to any one type of dataset in Digital Coast.   For example, topobathy lidar data may cover the footprint displayed in DAV but it may not necessarily contain points for a class that you selected during the checkout process.   Essentially, there is data but just not the data that you want.  Asking for ground points in the water or bathy points where there is only land is likely to lead to sorrow.

Although rare, we do see no-data error messages from DAV for raster requests.  This is most often attributed to users drawing a box where there is imagery for part of a tile (Figure 1).  This is partly due to flightline orientation and the mosaic process.  The folks working with DAV are starting to incorporate a new method for creating footprints that will only encompass the portion of the image that has data.  It will not include the no-data values (often displayed as black).  They are also creating image services so that the image displays in DAV (Figure 1).  I don’t know about ya’ll but I love being able to see the data before downloading it.  These improvements should reduce or eliminate error messages associated with this problem (and if you do get the data because the box you drew contained a sliver of data, this should explain why the majority of the image has mostly black pixels).

Figure 1.  The yellow box is my area of interest.  It appears that data exists since it is within the blue image boundary.  However, when you look at the image itself, you can see that there is no imagery available.

There are a few other common problems mentioned in an earlier post. These still crop up, although they’ve been reduced in the new DAV interface. Some requests are still going to break things.

If you don’t get data you were expecting in a timely manner, don’t panic.  First, check your spam folder.  If you don’t have any luck there, then double check the processing details from the confirmation email that Digital Coast sent you.   It will let you know the status of your job.   If you still have problems or something just isn’t right with the data, then send an email to ocm.dds@noaa.gov alerting them of the issue/concern.  There is a good chance that they are aware of the issue and can provide you with more details about what caused the fail whale.

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