In response to a request from two U.S. Congressmen on how location-based service data is collected and shared, Apple offered a surprisingly open and detailed response. The questions were presented to the Cupertino-based company by Representative Joe Barton (D, Texas) and Edward Markey (D, Mass), who released Apple’s response on Monday.

“When a customer’s device sends Wi-Fi, cell tower, GPS, or diagnostic location information to Apple, it does not include any information identifying the particular device or user,” Apple General Counsel Bruce Sewell told the Congressmen in his written response.

He added that any information that’s collected is maintained for six months, but that location-based data that’s passed on to partners is converted from latitude and longitude into ZIP codes.

The Congressmen asked Apple for clarification on how data location-based services is collected and maintained after the company changed its policy in June to allow for aggregating information and sharing it with partners.

“It is imperative that consumers have control over how their personal information is used, transmitted, and stored,” Rep. Markey said. “Apple’s responses provided additional information about how it uses location data and the ability of consumers to exercise control over a variety of features on Apple’s products, and I appreciate the company’s response.”

Rep. Barton added “Consumer consent is the key to assessing the adequacy of privacy protections, and Apple’s responses provide examples of how consumers can grant or withhold consent in their usage of Apple products.”

Apple confirmed users can opt out of sharing location-based information by not agreeing to the policy changes, although they won’t be able to create an iTunes Store account if they do so. Alternately, users can disable location-based services on the iPhone, iPod touch or iPad by going to Settings > General > Location Services, and turning the feature off on a per-app basis or system-wide.

“A couple of fundamental principles must guide all decisions in this space: transparency, consumer consent, and consumer control,” Rep. Markey said. “I hope every business that uses information for advertising and marketing purposes will work toward more transparency and complete disclosure about their practices, as well as robust security for the information they hold.”

The full text of Apple’s response is available in PDF format at Rep. Markey’s Web site.

[Thanks to CNET for the heads up.]