Here is an example of how you can use an SD card to store GPS data on an ESP8266 and serve files from the SD card on an access point web server:

    First, you will need to connect the SD card to the ESP8266. This can typically be done using an SD card module, such as the popular SD library.

#include <SD.h>

const int chipSelect = D5;

void setup() {
    pinMode(chipSelect, OUTPUT);
    if (!SD.begin(chipSelect)) {
        Serial.println("SD card initialization failed!");
        return;
    }
    Serial.println("SD card initialized.");
}

    Next, you will need to read the GPS data from the serial port and write it to a file on the SD card. Here is an example of how to do this:

void loop() {
    if (Serial.available()) {
        String gpsData = Serial.readString();
        File dataFile = SD.open("gpsData.txt", FILE_WRITE);
        if (dataFile) {
            dataFile.println(gpsData);
            dataFile.close();
            Serial.println("GPS data written to file.");
        } else {
            Serial.println("Error opening file for writing.");
        }
    }
}

    To serve the files from the SD card on an access point web server, you will need to use the ESP8266WebServer library. Here is an example of how to do this:

#include <ESP8266WebServer.h>

ESP8266WebServer server(80);

void setup() {
    //initialize SD card, WiFi, etc.
    server.on("/", handleRoot);
    server.onNotFound(handleNotFound);
    server.begin();
    Serial.println("Server started");
}

void handleRoot() {
    File root = SD.open("/");
    String output = "Files:<br>";
    while (true) {
        File entry = root.openNextFile();
        if (!entry) {
            break;
        }
        output += "<a href='";
        output += entry.name();
        output += "'>";
        output += entry.name();
        output += "</a><br>";
        entry.close();
    }
    server.send(200, "text/html", output);
}

void handleNotFound() {
    File file = SD.open(server.uri());
    if (file) {
        server.streamFile(file, "application/octet-stream");
        file.close();
    } else {
        server.send(404, "text/plain", "404: Not Found");
    }
}

This example creates an instance of the ESP8266WebServer class on port 80, and sets up two routes: one to handle requests to the root URL, which lists the files on the SD card, and another to handle requests for any other URLs, which serves the requested file from the SD card.

Please note that this is just an example and you may need to adapt it to your specific use case. Also note that the access point creation is not included