This section is where you tell NASA SkyWatch where you are. The inputs are your geodetic latitude in decimal degrees, your longitude in decimal degrees, the number of hours from Greenwich Mean Time to your local time and a Daylight Savings Time checkbox.
The geodetic latitude and longitude are those values commonly found on maps and charts. The values are entered in decimal degrees. Northern latitudes are entered as positive and Southern latitudes are entered as negative. Similarly, Eastern longitudes are entered as positive and Western longitudes are entered as negative.
The location of the zip code 77058 in Houston, Texas is 29 degrees 33 minutes and 13.92 seconds North latitude and 95 degrees 5 minutes and 43.36 seconds West longitude. To enter this location into SkyWatch you will need to convert these values to decimal degrees as follows:
Latitude: 29 + 33/60 + 13.92/3600 = 29.5538 degrees
Longitude -(95 + 5/60 + 43.36/3600) = -95.0950 degrees
It is not required for extreme precision when you input your location since the acquisition information that you will generate will still be valid even if you are many miles off. However, the closer you get to your exact location, the more precise the results will be.
The number of hours from Greenwich Mean Time, or GMT, to your local time is entered so that the output table will indicate the correct local time and date of your location for acquisition data. Check the "Daylight Savings" checkbox if you are currently under daylight-saving time. For example, if you live in Houston, Texas, you are six hours behind GMT so the GMT to local conversion would be -6 hours. If it is the summer and you are using daylight-saving time, check the "Daylight Savings" checkbox to add one hour to the conversion. The value in the conversion box will not change, but the table will reflect the correct local time. Entering -5 hours for the conversion and not selecting the checkbox will have the same effect.
Unsure of your exact latitude, longitude or number of hours from GMT? Enter the zip code of the location you require and NASA SkyWatch will provide you with the information.
If you prefer an international city, check the pull down selection of cities that NASA SkyWatch provides. Simply click on the city, town or one that is closest to the desired location, and NASA SkyWatch will provide you with the information.
Curator: Kim Dismukes | Responsible NASA Official: Amiko Kauderer | Updated: 09/23/2011