Polar Explorer

Polar Explorer: Sea Level App© Frequently Asked Questions

How do I obtain the instructions to use this app?

Press the New User icon in the lower center of the screen upon opening the app. Or find its link within the app on the Polar Explorer Home Page.

How do I pan and zoom?

Pan by dragging a single finger in contact with and across the screen and zoom by squeezing or expanding two fingers also in contact with the screen.

Why does the map image not update when panning or zooming?

Make sure you are connected to Wi-Fi or with 3G for the iPhone and 3G-enabled iPad. An internet connection is mandatory to fetch content.

App starts by displaying a negative image of earth landscape and will not respond or do anything. Then after about 30 seconds it exits.

The Wi-Fi or 3G connection is too weak or intermittant. The app is unable to fetch the necessary content to successfully initiate. In the next relasae this situation will provide a warning, rather than exiting.

Why is the content changing slowly?

Most likely due to limited bandwith, a weak wireless signal, the result of server overload or the attempt to fetch more than 5 MB of tiles within the span of a five minute period using a 3G connection.

What does the green border to the map indicate?

The green border indicates that there is more content available at higher zoom levels.The green border appears even if the application is unsuccessful in uploading (refreshing) tiles while panning and zooming. In this case you most likely lack a satisfactory WiFi or 3G connection. Check the Status icon on the left in the top banner of the device to ascertain the presence and strength of the signal.

What does a red border on the map indicate?

The maximum zoom level (image resolution) has been reached for the current content.

What do the yellow lines within the map indicate?

These lines are borders of tiles being requested from the server. The lines disappear as soon as the required tiles have been fetched successfully.

How do I find a list of available content?

Press the > in the lower left region of the screen to bring up a Menu Panel.

How do I select content?

Open the Menu Panel by pressing the > icon in the lower right corner of the map. Then press a title (layer name) on the scrollable list in the Menu Panel. If the title is followed by an arrow, the action opens a descendant (daughter) Menu Panel with choices of layers related in theme to the parent layer. To confirm a successful selection, the title region darkens and a check mark appears to the right of the title. Pressing the Done button returns to the map with the selected layer displayed as an overlay on the Basemap.

How do I find further information about a layer in the Menu Panel?

Press the i icon to the left of the layer title to open a browser window containing content description, data sources, credits, citations and external links.

What if the browser window remains blank without content after opening?

You are either not connected to a Wi-Fi network, the Wi-Fi signal is too weak to successfully fetch the document, or you are not connected using 3G on the iPhone or 3G-enabled iPad, or its signal has dropped out. Check the Status icon in the topmost panel of the device to ascertain the presence and strength of the signal.

Does pressing the i icon select the layer?

No. You must touch the title (layer name) to select a layer.

What do I do if nothing happens after touching the i icon?

Try wetting the tip of your finger and touching the i icon again to improve the contact with the screen.

How do I change the opacity (transparency) of a displayed layer?

Drag the small circular button along the slider bar in the map window.

Can I change the opacity of the Basemap layer?

No. The opacity (transparency) of the Basemap can not be changed.

Can I superimpose the Basemap on other layers?

No. The Basemap always remains under other selected layers and can not superimposed on any other layer.

Can a selected layer be superimposed on another selected layer?

No. Due to the current limited graphics memory in the device, only one layer at a time can be superimposed on the Basemap layer, including overlays for coastlines, country boundaries, etc.

What if I do not want to select a descendant (daughter) layer?

Press the Back button in the descendant (daughter) Menu Panel to return to the Parent Menu Panel or press the Done button to return to the map view.

How do I dispose of a selected layer?

Select another topic from the Menu Panel.

How do I find either a numerical value or text description at a location in a selected layer?

Tap the spot with a single finger tip. A small triangle appears with the notation above. The apex of the triangle marks the spot tapped.

What if tapping does not return a value or description?

You may have tapped in a transparent region without content (indicated by colored pixels).

How do I disable the display of geographic names?

Press the Gear-shaped icon at the bottom of the Menu Panel to open the Preferences Panel. Move the corresponding switch from On to Off. Press the Done button to return to the Menu Panel.

How do I disable the display of scale bars?

Press the Gear-shaped icon at the bottom of the Menu Panel to open the Preferences Panel. Move the corresponding switch from On to Off. Press the Done button to return to the Menu Panel.

How do I disable the display of legends superimposed on the map?

Press the Gear-shaped icon at the bottom of the Menu Panel to open the Preferences Panel. Move the corresponding switch from On to Off. Press the Done button to return to the Menu Panel.

Why do some legends appear on the iPad but not on the iPhone or iPod touch?

Legends that occupy a large regions of the map on these small screens are purposely not shown. They can be seen in the browser upon selecting the i icon next to the layer name in menu panel.

What if the names, scalebars and legends reappear without re-enabling them in the Preferences Panel?

Currently you must turn them off again using the Preferences Panel. We are evaluating user response to learn if these should be on automatically every time the app is re-opened or should remain off until intentionally switched back on. We do not want users to forget that legends, scalebars and names are available.

What is the Basemap layer?

The basemap consists of equally-spaced, sun-illuminated elevations on land and sun-illuminated depths for the oceans and seas. The illumination is computer-generated and directed from the upper left. For land regions the elevations and their shading derive from gridded digital elevation models (DEMs). We use DEMs obtained from the ASTER satellite mission for the land regions at approximastely 30 m grid-node resolution and DEMs from the National Elevation Dataset at 10 m grid-node separation for the US mainland and Hawaii and 25 m for Alaska, Puerto Rico and Mexico. For the oceans we use the GEBCO_08 global bathymetric grid at 30 arc-seconds (~1 km) grid-node separation supplemented by high-resolution digital multibeam echo-sounding surveys down to 50 m grid-node separation for deep regions and to 4 m grid-node separation for some coastal areas and harbors.

What about my privacy concerns?

We monitor the delivery of content to ascertain the load on our servers for which we pay a service fee. No information is preserved or distributed to identify users or their specific internet addresses. We tabulate the content retrieved from the servers so as to communicate the usage to data providers. This information helps us obtain future funding to develop more content and aids in the support of researchers, teams and agencies who generate data and make their results available.

Offered by the Polar Explorer team at the Lamont-Doherty Earth Observatory of Columbia University