get geoid as javascript function

[kfarr]

Good news -- we now have what appears to be a working method to reliably find the ground point of google 3d tiles for a 3DStreet scene.

However, how can we offer this updated feature without breaking existing user's geospatial scenes?

How we store elevation today:

• "elevation" value is stored in street-geo component
• this value is fetched from google elevation service which returns topographical elevation
• street-geo adds an arbitrary hack constant (32.49158) to convert topographical height to ellipsoidal height. Using a constant value is incorrect (outside of the SF Bay Area). Instead, ellipsoidalHeight value can be calculated only with geoid height which varies based on user-specified lat/lon.

change:

• now we have the a more accurate ellipsoidalHeight from our new cloud function (yay!), but how should we handle this new feature without breaking old stored user values?

proposed way to handle to be backwards compatible:

• add new property to street-geo component ellipsoidalHeight
• if ellipsoidalHeight exists, then use that value for google3d tiles without the hack constant
• if it doesn't, then use old school elevation value with the existing hack constant

how to do this?

• add 2 conditional statements in street-geo init and update methods:

    // if data.ellipsoidalHeight, use it, otherwise use data.elevation less constant (deprecated)
    const height = data.ellipsoidalHeight
      ? data.ellipsoidalHeight
      : data.elevation - this.elevationHeightConstant;

test scenarios:

• user makes a new geospatial scene which automatically specifies ellipsoidalHeight for new locations; elevation may be null, NaN, 0, we don't care; correct ground location should "just work" with max adjustment of ~2 meters needed
• user opens a existing geospatial scene -- the elevation value is technically incorrect but the user has manually adjusted their scene to match the naive constant method; what do we want to happen? we want existing behavior
• what happens when a user edits the location of an existing geospatial scene? we want it to use the new, correct value.
• what happens if opens an old geospatial scene, makes edits but NOT to the geospatial settings? the user expects the 3dtiles "to stay where they are" so let's make sure they do!
• what happens if an ellipsoidalHeight value is actually 0 -- will javascript assume that the value is falsy and use the incorrect (or nonexistent) elevation value?

other issues need to fix:

• does not allow for negative numbers for ellipsoidal value

[kfarr]

although this worked in local emulator, fun new error from firebase when trying to deploy:
Error: [getGeoidHeight(us-central1)] Changing from an HTTPS function to a callable function is not allowed. Please delete your function and create a new one instead.

• does this mean i should rename it, or "delete" from a gui?

answer: delete from gui and then deploy

[rahulkgupta]

I'm having trouble following the description. For user's stored values, can't we just use that and not rely on the service?

"elevation" value is stored in street-geo component
this value is fetched from google elevation service which returns topographical elevation

What does this mean? Is the value stored in the scene data in the firebase db or is it fetched via google elevation?